Styrene-free copolymers and coating compositions containing such copolymers

ABSTRACT

An aqueous coating composition is provided that is preferably substantially free of styrene and structural units derived from styrene. The coating composition includes a resin system that preferably includes a water-dispersible polymer and an emulsion polymerized ethylenically unsaturated monomer component. The resin system is preferably formed using a process that includes emulsion polymerizing the ethylenically unsaturated monomer component in the presence of an aqueous dispersion including the water-dispersible polymer. In certain preferred embodiments, the water-dispersible polymer is a salt of an acid- or anhydride-functional aromatic polyether polymer.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a continuation under 35 U.S.C. § 111 of applicationSer. No. 16/160,579 filed Oct. 15, 2018 and scheduled to issue Dec. 10,2019 as U.S. Pat. No. 10,501,639 B2, which is a continuation under 35U.S.C. § 111 of International Application No. PCT/US2017/027453 filedApr. 13, 2017, which claims priority under 35 U.S.C. § 119 to and thebenefit of U.S. Provisional Application No. 62/323,314 filed Apr. 15,2016, each of which is entitled “STYRENE-FREE COPOLYMERS AND COATINGCOMPOSITIONS CONTAINING SUCH COPOLYMERS” and the disclosures of each ofwhich are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Bisphenol A has been used to prepare polymers having a variety ofproperties and uses. For example, bisphenol A may be reacted withepichlorohydrin to provide polymers useful in packaging coatings. Thereis a desire to reduce or eliminate the use of certain bisphenolA-derived polymers in food or beverage container coatings. Although anumber of replacement coating compositions made without bisphenol A havebeen proposed, some replacement compositions have exhibited insufficientcoating properties such as insufficient corrosion resistance on metalsubstrates, insufficient flexibility or insufficient toughness.

In addition, in recent years styrene has also come under greaterscrutiny. Although the balance of scientific evidence indicates thatcoatings containing polymerized styrene are safe for food-contact enduses, there is a desire by some to eliminate styrene from such end uses.Styrene, however, brings advantageous properties that contribute to theoverall performance of food or beverage can coatings and can bedifficult to replicate using other materials. As such, the use ofstyrene in conventional such coatings has been commonplace.

The balance of coating performance attributes required for a coatingcomposition to be suitable for use as a food or beverage can coatingsare particularly stringent and are unique from other coating end uses.As such, coatings designed for other ends uses are not typicallysuitable for use as food or beverage can coatings.

For example, coatings for use on food or beverage containers shouldavoid unsuitably altering the taste of the packaged food or beverageproducts, and should also avoid flaking or chipping into the packagedproducts. The coatings should also resist chemically aggressive food orbeverage products (which can have a complex chemical profile, includingsalt, acids, sugars, fats, etc.) for extended periods of time (e.g.,years). Food or beverage container coatings should also have goodadhesion to the underlying substrate and remain sufficiently flexibleafter curing, because subsequent fabrication and denting duringtransportation, storage or use (e.g., by dropping) may cause the metalsubstrate to deform, which will cause the coating to flex. A brittlecoating will crack during flexure, exposing the container metal to thepackaged products, which can sometimes cause a leak in the container.Even a low probability of coating failure may cause a significant numberof containers to leak, given the high number of food and beveragecontainers produced.

Accordingly, it will be appreciated that what is needed in the art areimproved coating compositions that are made without intentionally usingbisphenol A and/or styrene, but which exhibit the stringent balance ofcoating properties to permit the use of such coating compositions onfood or beverage containers.

SUMMARY

In one aspect, the present invention provides an aqueous coatingcomposition. In preferred embodiments, the coating composition is anaqueous food or beverage can coating composition suitable for use informing a food-contact coating on a metal substrate of a food orbeverage can. The coating composition preferably comprises an aqueouscarrier and a resin system dispersed in the aqueous carrier. The resinsystem is preferably substantially free of styrene and comprises awater-dispersible polymer (e.g., a water-dispersible polyether polymer)and a polymerized ethylenically unsaturated monomer component, morepreferably an emulsion polymerized ethylenically unsaturated monomercomponent. In preferred embodiments, the polymerized ethylenicallyunsaturated monomer component includes: (a) one or more alkyl(meth)acrylates (and more preferably at least 30 wt-% of one or morealkyl (meth)acrylates) and (b) one or more ethylenically unsaturatedmonomers having a cycloaliphatic group or a linear or branchedhydrocarbon group including at least 4 carbon atoms (more preferablymore than 30 wt-% of one or more ethylenically unsaturated monomershaving a cycloaliphatic group or a linear or branched hydrocarbon groupincluding at least 4 carbon atoms). Typically, the polymerizedethylenically unsaturated monomer component will include at least onemethacrylate, and in some embodiments 50 wt-% or more of one or moremethacrylates.

In yet another aspect, the present invention provides an aqueous food orbeverage can coating composition that preferably comprises an aqueouscarrier and a resin system dispersed in the aqueous carrier, wherein theresin system is preferably substantially free of styrene and comprises awater-dispersible polymer (e.g., a water-dispersible aromatic polyetherpolymer) and an emulsion polymerized ethylenically unsaturated monomercomponent that preferably comprises at least a majority (e.g., >50wt-%, >60 wt-%, >70 wt-%, etc.), and more preferably at least 80 wt-%,of one or more (e.g., one, two, three, four, or five) of methylmethacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate (e.g.,n-butyl acrylate), and butyl methacrylate (e.g., n-butyl methacrylate).

In yet another aspect, the present invention provides an aqueous food orbeverage can that preferably comprises an aqueous carrier and a resinsystem dispersed in the aqueous carrier, wherein the resin system issubstantially free of styrene and comprises: (i) a water-dispersiblearomatic polyether polymer that is substantially free of each ofbisphenol A, bisphenol F, and bisphenol S, including epoxides thereofand (ii) an emulsion polymerized ethylenically unsaturated monomercomponent, which is preferably emulsion polymerized in the presence ofthe water-dispersible aromatic polyether polymer. The emulsionpolymerized ethylenically unsaturated monomer component preferablycomprises at least 50 wt-% of one or more alkyl or cycloaliphatic(meth)acrylates and more than 30 wt-% of one or more ethylenicallyunsaturated monomers having a linear or branched hydrocarbon group thatincludes at least four carbon atoms and has a chain length of at least 3carbon atoms. In preferred such embodiments, the total combined weightof the water-dispersible aromatic polyether polymer and the emulsionpolymerized ethylenically unsaturated monomer component is at least 50wt-% of the total resin solids present in the coating composition.

In yet another aspect, substrates (e.g., metal substrates) having acoating composition of the present invention disposed thereon are alsodisclosed. In some embodiments, the substrate is a metal food orbeverage can, or portion thereof (e.g., twist-off closure lid, can end,beverage can end, can sidewall and bottom end, etc.) with the coatingcomposition of the present invention applied on an exterior surface, aninterior surface, or a combination of both. Certain embodiments of thepresent invention have been found to be particularly suitable for sprayapplication on the interior of food or beverage cans, including, e.g.,aluminum beverage cans.

In yet another aspect, the present invention provides a method ofcoating a food or beverage can. The method preferably includes applyinga coating composition described herein to a surface of a metal substrateprior to or after forming the metal substrate into a food or beveragecan or a portion thereof.

In yet another aspect, the present invention provides latex dispersionsand methods of making latex dispersions. The latex dispersion ispreferably substantially free of each of: styrene, bisphenol A,bisphenol F, and bisphenol S, including epoxides thereof, and is alsooptionally substantially free of substituted styrene compounds. Inpreferred embodiments, the method includes providing an aqueousdispersion of a water-dispersible polymer, emulsion polymerizing anethylenically unsaturated monomer component in the presence of theaqueous dispersion of the water-dispersible polymer. In preferredembodiments, the ethylenically unsaturated monomer component comprises amixture of monomers that includes more than 30% by weight of one or moreethylenically unsaturated monomer having a cycloaliphatic group or afour carbon or longer hydrocarbon group, and optionally a C1-C3 alkyl(meth)acrylate. The ethylenically unsaturated monomer componentpreferably includes at least one alkyl (meth)acrylate, more preferablyat least one alkyl methacrylate. Alkyl (meth)acrylates preferablyconstitute at least 20 wt-%, at least 30 wt-%, at least 50 wt-%, atleast 70 wt-%, at least 95 wt-%, or even 99 wt-% or more of theethylenically unsaturated monomer component.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which can be used invarious combinations. In each instance, the recited list serves only asa representative group and should not be interpreted as limiting or asan exclusive list.

The details of one or more embodiments of the invention are set forth inthe description below. Other features, objects, and advantages of theinvention will be apparent from the description and from the claims.

SELECTED DEFINITIONS

Unless otherwise specified, the following terms as used herein have themeanings as provided below.

The term “mobile” when used with respect to a compound in a coatingcomposition means that the compound can be extracted from the coatingcomposition when a coating (typically ˜1 mg/cm²) is exposed to a testmedium for some defined set of conditions, depending on the end use.Examples of these testing conditions include exposure of the curedcoating to HPLC-grade acetonitrile for 24 hours at 25° C. Exemplaryprocedures and limits are set out in European Union CommissionDirectives 82/711/EEC, 93/8/EEC and 97/48/EC and in 21 CFR section175.300, paragraphs (d) and (e).

The term “on,” when used in the context of a coating applied on asurface or substrate, includes both coatings applied directly orindirectly to the surface or substrate. Thus, for example, a coatingapplied to a primer layer overlying a substrate constitutes a coatingapplied on the substrate.

Unless otherwise indicated, the term “polymer” includes bothhomopolymers and copolymers (e.g., polymers of two or more differentmonomers). Similarly, unless otherwise indicated, the use of a termdesignating a polymer class such as, for example, “polyether” isintended to include both homopolymers and copolymers (e.g.,polyether-ester copolymers).

A group that may be the same or different is referred to as being“independently” something. The term “group” also encompasses single atommoieties. Thus, for example, a halogen atom can be a group.

The terms “acrylate” and “acrylic” are used broadly herein andencompasses materials prepared from, for example, one or more of acrylicacid, methacrylic acid, or any acrylate or methacrylate compound. Thus,for example, a polyether-acrylate copolymer in which the “acrylate”component consists entirely of polymerized (meth)acrylic acid wouldstill include an “acrylate” component even though no (meth)acrylatemonomer was employed.

The term “(meth)” as used in “(meth)acrylate” and “(meth)acrylic acid”is intended to indicate that either a hydrogen or methyl group may beattached to the pertinent carbon atom of the monomer. For example “ethyl(meth)acrylate” encompasses both ethyl acrylate, ethyl methacrylate, andmixtures thereof.

The term “phenylene” as used herein refers to a six-carbon atom arylring (e.g., as in a benzene group) that can have any substituent groups(including, e.g., hydrogen atoms, hydrocarbon groups, oxygen atoms,hydroxyl groups, etc.). Thus, for example, the following aryl groups areeach phenylene rings: —C₆H₄—, —C₆H₃(CH₃)—, and —C₆H(CH₃)₂(OH)—. Inaddition, for example, each of the aryl rings of a naphthalene group arephenylene rings.

The term “polyhydric phenol” (which includes dihydric phenols) as usedherein refers broadly to any compound having one or more aryl orheteroaryl groups (more typically one or more phenylene groups) and atleast two hydroxyl groups attached to a same or different aryl orheteroaryl ring. Thus, for example, both hydroquinone and 4,4′-biphenolare considered to be polyhydric phenols. As used herein, polyhydricphenols typically have six carbon atoms in an aryl ring, although it iscontemplated that aryl or heteroaryl groups having rings of other sizesmay be used.

The term “polyhydric polyphenol” (which includes bisphenols) refers to apolyhydric phenol that includes two or more aryl or heteroaryl groupseach having at least one hydroxyl group attached to the aryl orheteroaryl ring.

The term “bisphenol” refers to a polyhydric polyphenol monomer havingtwo phenylene groups that each have a hydroxyl group attached to acarbon atom of the ring, wherein the rings of the two phenylene groupsdo not share any atoms in common. The term “polyhydric monophenol”refers to a polyhydric phenol that (i) includes an aryl or heteroarylgroup (more typically a phenylene group) having at least two hydroxylgroups attached to the aryl or heteroaryl ring and (ii) does not includeany other aryl or heteroaryl rings having a hydroxyl group attached tothe ring. The term “dihydric monophenol” refers to a polyhydricmonophenol that only includes two hydroxyl groups attached to the arylor heteroaryl ring.

The term “substantially free” when used with respect to a coatingcomposition that may contain a particular mobile compound means that thecoating composition contains less than 1,000 parts per million (ppm) ofthe recited mobile compound. The term “essentially free” when used withrespect to a coating composition that may contain a particular mobilecompound means that the coating composition contains less than 100 partsper million (ppm) of the recited mobile compound. The term “essentiallycompletely free” when used with respect to a coating composition thatmay contain a particular mobile compound means that the coatingcomposition contains less than 5 parts per million (ppm) of the recitedmobile compound. The term “completely free” when used with respect to acoating composition that may contain a particular mobile compound meansthat the coating composition contains less than 20 parts per billion(ppb) of the recited mobile compound. If the aforementioned phrases areused without the term “mobile” (e.g., “substantially free of BPAcompound”) then the compositions contain less than the aforementionedamount of the compound whether the compound is mobile in the coating orbound to a constituent of the coating. When the phrases “free of”(outside the context of the aforementioned phrases), “does not includeany” and the like are used herein, such phrases are not intended topreclude the presence of trace amounts of the pertinent structure orcompound which may be present, e.g., as environmental contaminants.

The term “styrene-free” indicates that styrene was not intentionallyused, although trace amounts of contaminating styrene may still bepresent. In the discussions that follow, for convenience, the phrase“styrene-free” may be replaced with “substantially free of styrene” toprovide a discrete threshold value.

The terms “preferred” and “preferably” refer to embodiments that mayafford certain benefits, under certain circumstances. However, otherembodiments may also be preferred, under the same or othercircumstances. Furthermore, the recitation of one or more preferredembodiments does not imply that other embodiments are not useful, and isnot intended to exclude other embodiments from the scope of theinvention.

The terms “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims.

As used herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably. Thus, for example, a coating composition thatcomprises “a” polyether polymer can be interpreted to mean that thecoating composition includes “one or more” polyether polymers.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.). Furthermore, disclosure of a range includesdisclosure of all subranges included within the broader range (e.g., 1to 5 discloses 1 to 4, 1.5 to 4.5, 4 to 5, etc.).

DETAILED DESCRIPTION

Aqueous coating compositions for use on food or beverage containers suchas, e.g., metal food or beverage cans have typically included at leastsome styrene-containing polymer. For example, both aqueous epoxy coatingsystems and latex coating systems for use in coating metal food orbeverage cans have typically incorporated one or more free radicalpolymerized ethylenically unsaturated monomer components that includestyrene (e.g., an “acrylic” polymer or component). The use of styrene insuch coating compositions has been advantageous for a variety ofreasons, including, for example, because styrene possesses both a highlevel of hydrophobicity and a relatively high glass transitiontemperature (“Tg”) (e.g., styrene homopolymer exhibits a Tg of about100° C.). Prior attempts to replace styrene in such aqueous food orbeverage can coatings have resulted in coating systems that eitherexhibit an unsuitable balance of coating properties for a food orbeverage container coating end use or that exhibit one or more coatingproperties that are substantially diminished relative to conventionalstyrene-containing systems.

The coating composition of the present invention is substantially freeof styrene, and is preferably also substantially free of each ofbisphenol A (“BPA”), bisphenol F (“BPF”), and bisphenol S (“BPS”),including epoxides thereof (e.g., the diglycidyl ether of BPA (“BADGE”),etc.). In preferred embodiments, the coating composition exhibits abalance of coating properties in food or beverage can coating end usesthat is comparable to conventional epoxy-acrylate coating systems thatutilize substantial amounts of both BPA and styrene. In certainpreferred embodiments, the coating composition is also substantiallyfree of substituted styrene compounds (e.g., alpha-methylstyrene, methylstyrenes (e.g., 2-methyl styrene, 4-methyl styrene, vinyl toluene, andthe like), dimethyl styrenes (e.g., 2,4-dimethyl styrene),trans-beta-styrene, divinylbenzene, and the like). In some embodiments,the coating composition is substantially free of vinyl aromaticcompounds.

The coating composition of the present invention is preferably anaqueous coating composition. In preferred embodiments, such aqueouscoating compositions preferably include both: (i) a water-dispersiblepolymer (preferably a water-dispersible polyether polymer, morepreferably a water-dispersible aromatic polyether polymer) and (ii) apolymerized ethylenically unsaturated monomer component. The above (i)and (ii) components are each preferably made using ingredients that donot include styrene (although trace amounts of unintentionally addedstyrene may potentially be present due to, e.g., environmentalcontamination, etc.), more preferably the coating composition as a wholeis made using ingredients that do not include styrene. In preferredembodiments, the coating composition is a latex dispersion and theethylenically unsaturated monomer component is emulsion polymerized inthe presence of an aqueous dispersion that includes thewater-dispersible polymer dispersed therein. The polymerizedethylenically unsaturated monomer component is typically a mixture oftwo or more different monomers that are preferably capable of freeradical initiated polymerization in an aqueous medium. For sake ofconvenience, hereinafter the “polymerized ethylenically unsaturatedmonomer component” is referred to as the “emulsion polymerizedethylenically unsaturated monomer component.”

In preferred embodiments, the emulsion polymerized ethylenicallyunsaturated monomer component includes one or more ethylenicallyunsaturated monomers that include a cycloaliphatic group or ahydrocarbon group including at least four carbon atoms (referred tocollectively hereinafter as “monomer component A” or “monomers A” forshort), or a mixture of both. Although any suitable ethylenicallyunsaturated monomer(s) A may be used, such monomers will typically bevinyl monomers such as, for example, alkyl (meth)acrylates, cycloalkyl(meth)acrylates, vinyl aromatics (including, e.g., aryl(meth)acrylates), vinyl esters, and the like. One or more heteroatomsmay optionally be present in the cycloaliphatic group or the C4 orgreater hydrocarbon group. In some embodiments, only carbon atoms andhydrogen atoms are present in the cycloaliphatic group or the C4 orgreater hydrocarbon group. The C4 or greater hydrocarbon group can haveany suitable structure, although linear chains or branched linear chainsare preferred in some embodiments, with linear or branched linear groupshaving a longest chain that includes at least 3 carbon atoms beingparticularly preferred in certain embodiments. Alkyl (meth)acrylateshaving the specified groups are examples of preferred such monomers A,although any suitable type or types of ethylenically unsaturatedmonomers having such groups may be used.

While not intending to be bound by any theory, it is believed that theinclusion of one or more ethylenically unsaturated monomers that includea cycloaliphatic group and/or a hydrocarbon group having at least fourcarbon atoms can, among other things, help impart a suitably high levelof hydrophobicity. It is believed that this may be desirable formultiple reasons such as, e.g., to enhance water resistance and/orretort resistance and help reduce partitioning of low concentrationflavorants present in certain aqueous packaged products (e.g., certaincolas) into the coating.

Examples of suitable C4 or greater hydrocarbon groups for inclusion inmonomers A include hydrocarbon groups having 4 or more, 5 or more, 6 ormore, 7 or more, or 8 or more carbon atoms, with preferred suchhydrocarbon groups being butyl, pentyl, hexyl, and isomers thereof(e.g., n-butyl, sec-butyl, t-butyl. etc.). Some specific examples ofsuch monomers A include: n-butyl (meth)acrylate, isobutyl(meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate,n-pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate,2-ethylhexyl (meth)acrylate, isodecyl methacrylate, 3,5,5-trimethylhexyl(meth)acrylate, derivatives and isomers thereof, and combinationsthereof. In some embodiments, C4 or greater hydrocarbon groups havingbetween 4 and 6 carbon atoms are preferred. While not intending to bebound by any theory, it is believed that the inclusion of an excessiveamount of monomers A having long linear carbon chains (e.g., C7 orgreater, and in certain instances C5 and/or C6) may result in anemulsion polymerized ethylenically unsaturated monomer component havingan unsuitably low glass transition temperature for certain internal cancoating applications. Any suitably cycloaliphatic group may be employedin monomers A, including, for example, cycloaliphatic groups having4-membered rings, 5-membered rings, 6-membered rings, or even 7-memberedrings or larger. The cycloaliphatic groups may also be monocyclic orpolycyclic (e.g., bicyclic, tricyclic, tetracyclic, etc.). Any suitablepolycyclic groups may be employed, including, for example, bridgedpolycyclic ring systems (e.g., norbornane groups), fused polycyclic ringsystems, or combinations thereof (e.g., tricyclodecane groups).Typically, the atoms making up the ring(s) will be carbon atoms,although as discussed above, one or more heteroatoms may also be presentin the ring. Examples of monomers A having a cycloaliphatic groupinclude cyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl(meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, isobornyl(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, variants and isomersthereof, and mixtures thereof.

In some embodiments, butyl (meth)acrylates are preferred monomers A. Insome embodiments, the ethylenically unsaturated monomer componentincludes both butyl acrylate and butyl methacrylate. In some suchembodiments, it may be preferable to use an excess amount of butylmethacrylate relative to the amount of butyl acrylate.

In some embodiments, at least one monomer A of the below Formula (I) isemployed:CH₂═C(R¹)—X_(n)—C(CH₃)_(t)(R²)_(3−t)wherein:

-   -   R¹ is hydrogen or an alkyl group, more typically hydrogen or a        methyl group;    -   n is 0 or 1, more typically 1;        -   X, if present, is a divalent linking group; more typically            an amide, carbonate, ester, ether, urea, or urethane            linkage; and even more typically an ester linkage of either            directionality (i.e., —C(O)—O— or —O—C(O)—);    -   t is 0 to 3;    -   each R², if present, is independently an organic group that may        optionally be itself branched, more typically an alkyl group        that may optionally include one or more heteroatoms (e.g., N, O,        P, Si, etc.); and    -   two or more R² may optionally form a cyclic group with one        another.

In some embodiments, t is 1 and the total number of carbon atoms presentin both R² groups is 6, 7, or 8. Examples of such monomers A include theVEOVA 9 (Tg 70° C.), VEOVA 10 (Tg −3° C.), and VEOVA 11 (Tg −40° C.)monomers commercially available from Hexion.

In some embodiments, t is 0, 1, or 2, and least one R² is a branchedorganic group, more typically a branched alkyl group. Thus, for example,in some embodiments, at least one R² is present that includes a tertiaryor quaternary carbon atom. The VEOVA 9 monomer is an example of such abranched monomer.

In the discussions contained herein, various weight percentages areprovided pertaining to the constituents of the emulsion polymerizedethylenically unsaturated monomer component. As will be understood byone of skill in the art, unless specifically indicated to the contrary,these weight percentages are based on the total weight of the monomersused to form the emulsion polymerized ethylenically unsaturated monomercomponent.

In preferred embodiments, the emulsion polymerized ethylenicallyunsaturated monomer component includes more than 30 weight percent(“wt-%”), preferably at least 35 wt-%, more preferably at least 40 wt-%,and even more preferably at least 45 wt-% of one or more monomers A.While not presently preferred, in some embodiments, it may be possibleto use less than 30 wt-% of such monomers (e.g., at least 20 wt-% ofmonomers A) depending upon the balance of other monomers employed.Although the upper amount is not restricted, typically the ethylenicallyunsaturated monomer component will include less than 100 wt-%, moretypically less than 80 wt-%, even more typically less than 75 wt-%, andeven more typically less than 65 wt-% of one or more monomers A.

Any combination of one or more (meth)acrylates may be included in theethylenically unsaturated monomer component. Suitable (meth)acrylatesinclude any of those referenced herein, as well as those having thestructure of the following Formula (II): CH₂═C(R³)—CO—OR⁴ wherein R³ ishydrogen or methyl, and R⁴ is an alkyl group preferably containing oneto sixteen carbon atoms, a cycloaliphatic group, an aryl group, a silanegroup, or a combination thereof. If desired, R⁴ may optionally besubstituted with one or more (e.g., one to three) moieties such ashydroxy, halo, phenyl, and alkoxy, for example. Examples of suitable(meth)acrylates (including, e.g., suitable alkyl (meth)acrylates)include methyl (meth)acrylate, ethyl (meth)acrylate, propyl(meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl(meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, hexyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate,decyl (meth)acrylate, isodecyl (meth)acrylate, benzyl (meth)acrylate,phenyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate,octyl (meth)acrylate, nonyl (meth)acrylate, hydroxyethyl (meth)acrylate,hydroxypropyl (meth)acrylate, and the like, substituted variants thereof(e.g., ring substituted variants of benzyl (meth)acrylate or phenyl(meth)acrylate), and isomers and mixtures thereof.

In certain preferred embodiments, with respect to any (meth)acrylatesincluded in the emulsion polymerized ethylenically unsaturated monomercomponent, each R³ is independently hydrogen or methyl and each R⁴ isindependently a cycloalkyl group or an alkyl group having two to eightcarbon atoms. In some embodiments, each R³ is independently hydrogen ormethyl and each R⁴ is independently an alkyl group having two to fourcarbon atoms.

Typically, (meth)acrylates (e.g., one or a mixture of two or more(meth)acrylates) will constitute a substantial portion of the emulsionpolymerized ethylenically unsaturated monomer component. In someembodiments, (meth)acrylates may constitute at least 20 wt-%, at least30 wt-%, at least 50 wt-%, at least 70 wt-%, at least 95 wt-%, or even99 wt-% or more of the emulsion polymerized ethylenically unsaturatedmonomer component. The aforementioned weight percentages include all(meth)acrylates monomers present in the emulsion polymerizedethylenically unsaturated monomer component, regardless of whether oneor more of the monomers may also qualify as a “monomer A”. In someembodiments, one or more methacrylate monomers are present in theethylenically unsaturated monomer component in an amount recited in thisparagraph.

In some embodiments, alkyl (meth)acrylates may constitute at least 20wt-%, at least 30 wt-%, at least 50 wt-%, at least 70 wt-%, at least 95wt-%, or even 99 wt-% or more of the emulsion polymerized ethylenicallyunsaturated monomer. The aforementioned weight percentages include allalkyl (meth)acrylates monomers present in the emulsion polymerizedethylenically unsaturated monomer component, regardless of the fact thatall such monomers are also (meth)acrylates, and regardless of whetherone or more of the monomers may also qualify as a “monomer A”.

In some embodiments, a majority (e.g., >50 wt-%, ≥60 wt-%, ≥70 wt-%, ≥80wt-%, ≥90 wt-%, ≥95 wt-%, etc.), or even all, of the (meth)acrylatespresent in the emulsion polymerized ethylenically unsaturated monomercomponent are methacrylates, more preferably alkyl methacrylates.Examples of preferred methacrylates include methyl methacrylate, ethylmethacrylate, n-propyl methacrylate, n-butyl methacrylate, and isomersthereof (e.g., t-butyl methacrylate, iso-butyl methacrylate, etc.). Insome embodiments, the emulsion polymerized ethylenically unsaturatedmonomer component includes both n-butyl methacrylate and ethylmethacrylate. In some such embodiments, the emulsion polymerizedethylenically unsaturated monomer component includes at least: (i)n-butyl methacrylate and ethyl methacrylate and (ii) one or more alkylacrylates, more typically one or more “lower Tg” alkyl acrylate monomers(e.g., homopolymer Tg≤50° C., ≤40° C., ≤30° C., ≤20° C., ≤10° C., ≤0°C., ≤−10° C., or ≤−20° C.) such as ethyl acrylate (Tg −22° C. for itshomopolymer), n-propyl acrylate (Tg −37° C. for its homopolymer), methylacrylate (Tg 10° C. for its homopolymer), and/or n-butyl acrylate (Tg−54° C. for its homopolymer). Thus, in some embodiments, it may bedesirable to include one or more ethylenically unsaturated monomers,such as one or more alkyl(meth)acrylates, more typically one or morealkyl acrylates, which have a homopolymer Tg of less than 0° C. (or lessthan any of the other Tg value's referenced above).

In some embodiments, the emulsion polymerized ethylenically unsaturatedmonomer component includes one or more ethylenically unsaturatedmonomers having a C1-C3 hydrocarbon group. The methyl group attached tothe alpha-carbon of methacrylic acid is not considered such a C1-C3hydrocarbon group. Similarly, the vinylic group of a vinyl monomer isnot considered to be present in such a C1-C3 hydrocarbon group.Preferred such hydrocarbon groups include methyl, ethyl, propyl, andisopropyl groups. Examples of such monomers include alkyl(meth)acrylates in which the alkyl group (e.g., R⁴ group in aboveFormula (II)) is a C1-C3 alkyl group such as, e.g., methyl, ethyl,n-propyl, iso-propyl, and mixtures thereof. Preferred such monomershaving a C1-C3 hydrocarbon group include methyl methacrylate, ethylacrylate, ethyl methacrylate, and mixtures thereof. The emulsionpolymerized ethylenically unsaturated monomer component can include anysuitable amount of such monomers, including, for example at least 10wt-%, at least 20 wt-%, at least 30 wt-%, or at least 40 wt-%.Typically, the one or more ethylenically unsaturated monomers having aC1-C3 hydrocarbon group will constitute less than 70 wt-%, moretypically less than 65 wt-%, and even more typically less than 60 wt-%.In some embodiments, the emulsion polymerized ethylenically unsaturatedmonomer component includes from about 45 to about 55 wt-% ofethylenically unsaturated monomers having a C1-C3 hydrocarbon group.

Difunctional (meth)acrylate monomers may be used in the emulsionpolymerized ethylenically unsaturated monomer component as well.Examples include ethylene glycol di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, allyl methacrylate, butanediol di(meth)acrylate, andthe like.

In some embodiments, the emulsion polymerized ethylenically unsaturatedmonomer component may include a small amount (e.g., less than 5 wt-%,less than 2 wt-%, or less than 1 wt-%) of acid- or anhydride-functionalethylenically unsaturated monomer. Examples of suitable such acid- oranhydride-functional monomers may include any of those disclosed for usein conjunction with the acrylate portion of any of thepolyether-acrylate copolymers disclosed herein.

The ethylenically unsaturated monomer component may also include anyother suitable monomers. For example, suitable other vinyl monomers mayinclude isoprene, diallylphthalate, conjugated butadiene, vinylnaphthalene, acrylonitrile, (meth)acrylamides (e.g., acrylamide,methacrylamide, N-isobutoxymethyl acrylamide, N-butoxymethyl acrylamide,etc.), methacrylonitrile, vinyl acetate, vinyl propionate, vinylbutyrate, vinyl stearate, and the like, and variants and mixturesthereof.

In some embodiments, the emulsion polymerized ethylenically unsaturatedmonomer component does not contain any oxirane-group containing monomer.

In presently preferred embodiments, the emulsion polymerizedethylenically unsaturated monomer component does not include anyacrylamide-type monomers (e.g., acrylamides or methacrylamides).

The emulsion polymerized ethylenically unsaturated monomer component mayoptionally include one or more vinyl aromatic compounds other thanstyrene. Such vinyl aromatic compounds may be substituted styrenecompounds and/or other types of vinyl aromatic compounds (e.g., any ofthe aryl-group-containing ethylenically unsaturated monomers describedherein such as benzyl (meth)acrylate, etc.). In some embodiments, theemulsion polymerized ethylenically unsaturated monomer componentincludes, if any, less than 20 wt-%, less than 10 wt-%, less than 5 wt-%or less than 1 wt-% of vinyl aromatic compounds. In some embodiments,the emulsion polymerized ethylenically unsaturated monomer component issubstantially free of such compounds.

In some embodiments, the emulsion polymerized ethylenically unsaturatedmonomer component includes an amount of methyl methacrylate, if any, ofless than 10%, less than 20%, less than 40%, less than 50%, less than60%, or less than 70% by weight, based on the total weight of theemulsion polymerized ethylenically unsaturated monomer component.

Examples of some preferred monomer mixtures for the emulsion polymerizedethylenically unsaturated monomer component are provided in the belowtable. It should be noted that there is some overlap in the monomercategory descriptions. For example, butyl methacrylate is a monomer A,an alkyl (meth)acrylate, and a methacrylate. Moreover, monomer types notlisted in the table (e.g., aryl acrylates, ethylenically unsaturatedmonomers that are neither a (meth)acrylate or a monomer A, etc.) mayalso be included in the monomer mixtures.

Monomers included in ethylenically unsaturated Embodiment I EmbodimentII Embodiment III Embodiment IV monomer component (wt-%) (wt-%) (wt-%)(wt-%) Monomers A 30-100 35-80 40-75 45-65 C1-C3 alkyl 0-70 20-65 35-6040-55 (meth)acrylates Alkyl and/or 30-100  50-100  70-100  80-100cycloalkyl (meth)acrylates Methacrylates 20-100  50-100  60-100  70-100

The emulsion polymerized ethylenically unsaturated monomer component mayexhibit any suitable Tg value. In some embodiments, such as interior cancoatings that will be exposed to sensitive flavor products (e.g.,certain colas in which certain flavorants are present at very lowconcentrations) and/or chemically aggressive food or beverage products(e.g., highly acidic, high salt, and/or high fat), it may be desirableto use an emulsion polymerized ethylenically unsaturated monomercomponent having a Tg of greater than about 0° C., preferably greaterthan about 20° C., even more preferably greater than about 30° C., andeven more preferably greater than about 40° C. or greater than about 50°C. as determined by the Flory-Fox equation. In some embodiments, theemulsion polymerized ethylenically unsaturated monomer component mayeven have a Tg of greater than about 60° C. or greater than about 70° C.The Tg will typically be less than about 100° C., more typically lessthan about 90° C. as determined by the Flory-Fox equation. If theemulsion polymerized ethylenically unsaturated monomer componentincludes more than one stage, then the Flory-Fox equation should beapplied to the total monomer pool used (as opposed, e.g., to consideringeach monomer stage independently). If the emulsion polymerizedethylenically unsaturated monomer component includes more than 5% byweight of one or more monomers not having a homopolymer Tg (e.g.,because the monomer cannot be homopolymerized), then instead of relyingon the Flory-Fox equation, a single-stage reference latex can be madeusing the same overall monomer composition as the emulsion polymerizedethylenically unsaturated monomer component and the actual Tg measuredvia DSC. If the emulsion polymerized ethylenically unsaturated amountincludes 5% by weight or less of one or more monomers not having ahomopolymer Tg, then the one or more such monomers can be ignored andthe Tg determined by the Flory-Fox equation.

While it is contemplated that the ethylenically unsaturated monomercomponent may be polymerized separate from the water-dispersiblepolymer, in preferred embodiments, the ethylenically unsaturated monomercomponent is polymerized in an aqueous composition that includes thewater-dispersible polymer dispersed therein. Preferably, thewater-dispersible polymer functions as a “polymeric surfactant” thathelps support emulsion polymerization of the ethylenically unsaturatedmonomer component. Thus, in some embodiments, the ethylenicallyunsaturated monomer component is polymerized in the presence of thewater-dispersible polymer without the use of conventional non-polymericsurfactants (e.g., lower molecular weight surfactant such asamine-neutralized dodecyl benzene sulfonic acid or other suchconventional surfactants).

The water-dispersible polymer can be any suitable polymer or combinationof polymers including, for example, one or more acrylic polymers,polyester polymers, polyether polymers, polyolefin polymers,polysilicone polymers, polyurethane polymers, or copolymers thereof(e.g., polyether-acrylate copolymers, polyester-acrylate copolymers,etc.). The water-dispersible polymer may have any suitablewater-dispersing group or groups. Typically, the water-dispersiblepolymer will include one or more salt groups (e.g., anionic salts groupssuch as base-neutralized acid or anhydride groups) and/or salt-forminggroups (e.g., base groups and/or acid or anhydride groups). In preferredembodiments, the water-dispersible polymer is an acid- oranhydride-functional polymer in which preferably a suitable amount ofthe acid or anhydride groups have been neutralized with a suitable base,more preferably a fugitive base (e.g., nitrogen-containing bases such asammonia or amines).

In some embodiments, the water-dispersible polymer includes afree-radical polymerized ethylenically unsaturated monomer component(e.g., a styrene-free vinyl addition component). In preferred suchembodiments, the styrene-free vinyl addition component is formed from astyrene-free ethylenically unsaturated monomer mixture that includes oneor more acid- or anhydride-functional monomers (e.g., methacrylic acid)and typically one or more (meth)acrylates, more typically one or moremethacrylates, and even more typically one or more alkyl methacrylates(e.g., ethyl methacrylate and/or butyl methacrylate), optionally incombination with one or more acrylates and/or alkyl acrylates (e.g.,ethyl acrylate), wherein the monomer mixture is polymerized in organicsolvent in the presence or absence of the water-dispersible polymer. Insome embodiments, the water-dispersible polymer is a polyether-acrylatecopolymer, more preferably an aromatic polyether-acrylate that is freeof any structural units derived from styrene. In such embodiments, apolyether polymer used to form the polyether-acrylate copolymerpreferably comprises at least 30 wt-%, more preferably at least 50 wt-%,and even more preferably at least 60 wt-% or more of thepolyether-acrylate copolymer, based on the total weight of thepolyether-acrylate copolymer. Typically, the polyether polymer willconstitute less than 95 wt-%, more typically less than 90 wt-%, and evenmore typically less than 85 wt-% of the polyether-acrylate copolymer.

In some embodiments, the water-dispersible polymer may be a phosphatedpolymer. Examples of such water-dispersible polymers include reactionproducts of polymers having oxirane groups, preferably aromaticpolyether polymers having oxirane groups, and phosphoric acid or relatedcompounds. A specific example of such a water-dispersible polymer is anaromatic polyether phosphate ester polymer. Such phosphated polymers mayadditionally include one or more other salt groups to enable desiredmolecular weight and water-dispersity properties to be achieved.

The water-dispersible polymer can have any suitable molecular weight.Typically, the number average molecular weight of the water-dispersiblepolymer will be between about 1,500 and about 50,000, more typicallybetween about 2,000 and about 20,000.

In some embodiments, the polyether polymer has a Tg of at least 30° C.,more preferably at least 60° C., and even more preferably at least 70°C. or at least 80° C. Typically, the Tg of the polyether polymer will beless than 150° C., more typically less than 130° C., and even moretypically less than 110° C. In this context, the Tg refers to the Tgvalue of the polyether polymer alone (e.g., prior to forming apolyether-acrylate copolymer). Differential scanning calorimetry (DSC)is an example of a useful method for determining the Tg of the polyetherpolymer, with a representative DSC methodology provided later herein.

In embodiments in which the water-dispersible polymer is a polyetherpolymer or polyether-acrylate copolymer formed from ingredientsincluding a polyether polymer, the polyether polymer will typically havea number average molecular weight (Mn) of at least 2,000, more typicallyat least 3,000, and even more typically at least 4,000. The molecularweight of the polyether polymer may be as high as is needed for thedesired application. Typically, however, the Mn of the polyether polymerwill not exceed about 11,000. In some embodiments, the polyether polymerhas an Mn of about 5,000 to about 8,000. In embodiments where thewater-dispersible polymer is a polyether-acrylate copolymer, themolecular weight of the overall polymer may be higher than that recitedabove, although the molecular weight of the polyether polymer portionwill typically be as described above. Typically, however, suchpolyether-acrylate copolymers will have an Mn of less than about 20,000.

The water-dispersible polymers can include any suitable group orcombination of groups capable of rendering the polymer stablydispersible in an aqueous carrier liquid. The polymer of the aqueousdispersion can be made water-dispersible by incorporating non-ionicwater-dispersing groups, salt groups (e.g., anionic and/or cationic saltgroups), or a combination thereof. As used herein, the term“water-dispersing groups” also encompasses water-solubilizing groups.

Salt groups are preferred water-dispersing groups. Examples of suitablesalt groups include neutralized acid groups or neutralized base groups,with neutralized acid groups being presently preferred. Examples ofneutralized acid groups include carboxylic acid or anhydride groups thathave been at least partially neutralized with a suitable base. Fugitivebases are presently preferred, with nitrogen-containing bases beingpreferred, and amines (e.g., primary, secondary, and/or tertiary amines)being particularly preferred.

In certain embodiments, the amine is a tertiary amine. Preferably, thetertiary amine is selected from trimethyl amine, dimethylethanol amine(also known as dimethylamino ethanol), methyldiethanol amine, triethanolamine, ethyl methyl ethanol amine, dimethyl ethyl amine, dimethyl propylamine, dimethyl 3-hydroxy-1-propyl amine, dimethylbenzyl amine, dimethyl2-hydroxy-1-propyl amine, diethyl methyl amine, dimethyl1-hydroxy-2-propyl amine, triethyl amine, tributyl amine, N-methylmorpholine, and mixtures thereof. In certain preferred embodiments, anacid- or anhydride-functional polymer is at least 25% neutralized withthe amine in water.

A variety of acid- or anhydride-functional monomers, or salts thereof,can be incorporated into the water-dispersible polymer; their selectionis dependent on the desired final polymer properties. In someembodiments, such monomers are ethylenically unsaturated, morepreferably, alpha, beta-ethylenically unsaturated. Suitableethylenically unsaturated acid- or anhydride-functional monomers for thepresent invention include monomers having a reactive carbon-carbondouble bond and an acidic or anhydride group, or salts thereof.Preferred such monomers have from 3 to 20 carbons, at least 1 site ofunsaturation, and at least 1 acid or anhydride group, or salt thereof.

Suitable acid-functional monomers include ethylenically unsaturatedacids (e.g., mono-protic or diprotic), anhydrides or monoesters of adibasic acid, which are copolymerizable with the optional othermonomer(s) used to prepare the polymer. Illustrative monobasic acids arethose represented by the structure CH₂═C(R⁵)—COOH, where R⁵ is hydrogenor an alkyl group of 1 to 6 carbon atoms. Suitable dibasic acids includethose represented by the formulas R⁶(COOH)C═C(COOH)R⁷ andR⁶(R⁶)C═C(COOH)R⁸COOH, where R⁶ and R⁷ are each independently hydrogen,an alkyl group of 1 to 8 carbon atoms, a halogen, a cycloalkyl group of3 to 7 carbon atoms or a phenyl group, and R⁸ is an alkylene group of 1to 6 carbon atoms. Half-esters of these acids with alkanols of 1 to 8carbon atoms are also suitable.

Examples of useful ethylenically unsaturated acid-functional monomersinclude acids such as, for example, acrylic acid, methacrylic acid,alpha-chloroacrylic acid, alpha-cyanoacrylic acid, crotonic acid,alpha-phenylacrylic acid, beta-acryloxypropionic acid, fumaric acid,maleic acid, sorbic acid, alpha-chlorosorbic acid, angelic acid,cinnamic acid, p-chlorocinnamic acid, beta-stearylacrylic acid,citraconic acid, mesaconic acid, glutaconic acid, aconitic acid,tricarboxyethylene, 2-methyl maleic acid, itaconic acid, 2-methylitaconic acid, methyleneglutaric acid, and the like, or mixturesthereof. Preferred unsaturated acid-functional monomers include acrylicacid, methacrylic acid, crotonic acid, fumaric acid, maleic acid,2-methyl maleic acid, itaconic acid, 2-methyl itaconic acid, andmixtures thereof. More preferred unsaturated acid-functional monomersinclude acrylic acid, methacrylic acid, crotonic acid, fumaric acid,maleic acid, itaconic acid, and mixtures thereof. Most preferredunsaturated acid-functional monomers include acrylic acid, methacrylicacid, maleic acid, crotonic acid, and mixtures thereof.

Examples of suitable ethylenically unsaturated anhydride monomersinclude compounds derived from the above acids (e.g., as pure anhydrideor mixtures of such). Preferred anhydrides include acrylic anhydride,methacrylic anhydride, and maleic anhydride.

If desired, aqueous salts of the above acids may also be employed.

The water-dispersible polymer may have any suitable acid number so longas the polymer is preferably capable of being stably dispersed intowater. Preferred acid- or anhydride-functional water-dispersiblepolymers have an acid number of at least about 40, more preferably atleast about 55, and even more preferably at least about 70 milligrams(mg) KOH per gram of the polymer. While the upper range of suitable acidnumbers is not particularly restricted, typically the acid number willbe less than about 400, more typically less than about 300, and evenmore typically less than about 200 mg KOH per gram of the polymer. Acidnumbers referred to herein may be calculated pursuant to BS EN ISO3682-1998 standard, or alternatively may be theoretically determinedbased on the reactant monomers.

Polyether polymers are preferred water-dispersible polymers, witharomatic polyethers, which are preferably substantially free of each ofBPA, BPF, and BPS, including epoxides thereof, being particularlypreferred. Such polyether polymers typically include secondary hydroxylgroups, more typically secondary hydroxyl groups present in backbone—CH₂—CH(OH)—CH₂— segments. In preferred embodiments, the polyetherpolymer is derived from ingredients including (i) an aliphatic,cycloaliphatic, and/or aromatic diepoxide and (ii) an extender compoundcapable of building the molecular weight of the diepoxide to form apolymer. The above (i) and (ii) may be reacted together in anappropriate ratio such as, e.g., about 1.1:1 to about 1:1.1stoichiometric ratio.

Examples of suitable extender compounds include diols, diacids, andcompounds having both an acid and a hydroxyl group. Dihydric phenols arepreferred extenders, with polyhydric monophenols being preferred incertain embodiments. Examples of dihydric monophenol compounds includecatechol and substituted catechols (e.g., 3-methylcatechol,4-methylcatechol, 4-tert-butyl catechol, and the like); hydroquinone andsubstituted hydroquinones (e.g., methylhydroquinone,2,5-dimethylhydroquinone, trimethylhydroquinone,tetramethylhydroquinone, ethylhydroquinone, 2,5-diethylhydroquinone,triethylhydroquinone, tetraethylhydroquinone, tert-butylhydroquionine,2,5-di-tert-butylhydroquinone, and the like); resorcinol and substitutedresorcinols (e.g., 2-methylresorcinol, 4-methyl resorcinol,2,5-dimethylresorcinol, 4-ethylresorcinol, 4-butylresorcinol,4,6-di-tert-butylresorcinol, 2,4,6-tri-tert-butylresorcinol, and thelike); and variants and mixtures thereof.

Examples of suitable diepoxides include diepoxides of (e.g., diglycidylethers or esters of): substituted dihydric phenols (e.g.,ortho-substituted dihydric phenols such as tetramethyl bisphenol F,di-tert-butylhydroquinone, and the like), aromatic diols (e.g., benzenedimethanol, vanillyl alcohol, furane dimethanol, and the like), aromaticdiacids (e.g., isophthalic acid, terephthalic acid, and the like),aliphatic diols, aliphatic diacids, cycloaliphatic diols (e.g.,cyclobutane diols such as 2,2,4,4-tetramethyl-1,3-cyclobutanediol),cycloaliphatic diacids (e.g., cyclobutane diacids such as2,2,4,4-tetramethyl-1,3-cyclobutane dicarboxylic acid), and combinationsthereof.

In some embodiments, the water-dispersible polymer is a reaction productof ingredients including a dihydric phenol and a diepoxide of a dihydricphenol (e.g., reacted in an appropriate ratio such as, e.g., about 1.1:1to about 1:1.1 stoichiometric ratio).

Examples of suitable polyether polymers are disclosed in U.S. Pat. No.9,409,219, US2013/0206756, US2015/0021323, WO2015/160788, WO2015/164703,WO2015/057932, and WO2015/179064.

Polymers that are not reducible in water can be renderedwater-dispersible using technologies well known to those of skill in theart. In some embodiments, the polymer (e.g., aromatic polyether polymeror other polymer) is covalently attached to one or more materials (e.g.,monomers, oligomers or polymers) having one or more water-dispersinggroups (e.g., salt or salt-forming groups) to render the polymerwater-dispersible. The salt, salt-forming, or thewater-dispersible-group-containing material may be, for example,oligomers or polymers that are (i) formed in situ prior to, during, orafter formation of the polymer or (ii) provided as preformed materialsthat are reacted with a preformed, or nascent, polymer. The covalentattachment may be achieved through any suitable means including, forexample, via reactions involving carbon-carbon double bonds, hydrogenabstraction (e.g., via a reaction involving benzoyl peroxide mediatedgrafting via hydrogen abstraction such as, e.g., described in U.S. Pat.No. 4,212,781), or the reaction of complimentary reactive functionalgroups such as occurs, e.g., in condensation reactions. In oneembodiment, a linking compound is utilized to covalently attach thepolymer and a salt- or salt-forming-group-containing material. Incertain preferred embodiments, the one or more materials having salt orsalt-forming groups is a vinyl addition component (e.g., a vinyladdition polymer), which is typically an acrylic material (e.g., isformed from an ethylenically unsaturated monomer component that includesone or more of a (meth)acrylate, a (meth)acrylic acid, and the like),more preferably an acid- or anhydride-functional acrylic material.

In one embodiment, a water-dispersible polymer may be formed frompreformed polymers (e.g., (a) an oxirane-functional polymer, such as,e.g., an oxirane-functional polyether polymer, and (b) anacid-functional polymer such as, e.g., an acid-functional acrylicpolymer) in the presence of an amine, more preferably a tertiary amine.If desired, an acid-functional polymer can be combined with an amine,more preferably a tertiary amine, to at least partially neutralize itprior to reaction with an oxirane-functional polymer.

In another embodiment, a water-dispersible polymer may be formed from anoxirane-functional polymer (more preferably a polyether polymerdescribed herein) that is reacted with ethylenically unsaturatedmonomers to form an acid-functional polymer, which may then beneutralized, for example, with a base such as a tertiary amine. Thus,for example, in one embodiment, a water-dispersible polymer may beformed pursuant to the acrylic polymerization teachings of U.S. Pat.Nos. 4,285,847 and/or 4,212,781, which describe techniques for graftingacid-functional acrylic groups (e.g., via use of benzoyl peroxide) ontooxirane-functional polymers. In another embodiment, acrylicpolymerization may be achieved through reaction of ethylenicallyunsaturated monomers with unsaturation present in the polymer. See, forexample, U.S. Pat. No. 4,517,322 and/or U.S. Published Application No.2005/0196629 for examples of such techniques.

In another embodiment, a water-dispersible polymer may be formed havingthe structure E-L-A, where “E” is a polyether portion of the polymerformed from a polyether polymer, “A” is a polymerized acrylic portion ofthe polymer, and “L” is a linking portion of the polymer whichcovalently links E to A. Such a polymer can be prepared, for example,from (a) a polyether polymer preferably having about two oxirane groups,(b) an unsaturated linking compound preferably having (i) acarbon-carbon double bond, a conjugated carbon-carbon double bonds or acarbon-carbon triple bond and (ii) a functional group capable ofreacting with an oxirane group (e.g., a carboxylic group, a hydroxylgroup, an amino group, an amido group, a mercapto group, etc.).Preferred linking compounds include 12 or less carbon atoms, with sorbicacid being an example of a preferred such linking compound. The acrylicportion preferably includes one or more salt groups or salt-forminggroups (e.g., acid groups such as present in α,β-ethylenicallyunsaturated carboxylic acid monomers). Such polymers may be formed, forexample, using a BPA- and BADGE-free polyether polymers described inU.S. Pat. No. 9,409,219, US2013/0206756, US2015/0021323, WO2015/160788,WO2015/057932, or WO2015/179064 optionally in combination with thematerials and techniques disclosed in U.S. Pat. No. 5,830,952 orUS2010/0068433.

In the above approaches utilizing an acrylic component to render thepolymer water-dispersible, the acrylic component is typically formedfrom an ethylenically unsaturated monomer mixture that includes one ormore α,β-unsaturated carboxylic acid, although any suitable acid- oranhydride-functional monomer may be used. The one or moreα,β-unsaturated carboxylic acid preferably renders the polymerwater-dispersible after neutralization with a base. Suitableα,β-unsaturated carboxylic acid monomers include any of those previouslyreferenced herein.

The water-dispersible polymer (“a”) and the emulsion polymerizedethylenically unsaturated monomer component (“b”) can be employed in anysuitable weight ratio relative to one another. For example, the weightratio of (a):(b) can range from 10:1 to 1:10. In preferred embodiments,the weight ratio (a):(b) is from 40:60 to 90:10, more preferably 50:50to 80:20, and even more preferably 60:40 to 70:30.

With regard to the conditions of the emulsion polymerization, theethylenically unsaturated monomer component is preferably polymerized inaqueous medium with a water-soluble free radical initiator in thepresence of the water-dispersible polymer. Although not presentlypreferred, it is also contemplated that the emulsion polymerizedethylenically unsaturated monomer can be polymerized separately and thenlater mixed with the water-dispersible polymer.

The temperature of polymerization is typically from 0° C. to 100° C.,preferably from 50° C. to 90° C., more preferably from 70° C. to 90° C.,and even more preferably from 80° C. to 85° C. The pH of the aqueousmedium is usually maintained at a pH of 5 to 12.

The free radical initiator can be selected, for example, from one ormore water-soluble peroxides which are known to act as free radicalinitiators. Examples include hydrogen peroxide and t-butylhydroperoxide. Redox initiator systems well known in the art (e.g.,t-butyl hydroperoxide, erythorbic acid, and ferrous complexes) can alsobe employed. In some embodiments, a mixture of benzoin and hydrogenperoxide is used.

Further examples of polymerization initiators which can be employedinclude polymerization initiators that thermally decompose at thepolymerization temperature to generate free radicals. Examples includeboth water-soluble and water-insoluble species. Further examples of freeradical initiators that can be used include persulfates, such asammonium or alkali metal (potassium, sodium or lithium) persulfate; azocompounds such as 2,2′-azo-bis(isobutyronitrile),2,2′-azo-bis(2,4-dimethylvaleronitrile), and1-t-butyl-azocyanocyclohexane; hydroperoxides such as t-butylhydroperoxide, hydrogen peroxide, t-amyl hydroperoxide, methylhydroperoxide, and cumene hydroperoxide; peroxides such as benzoylperoxide, caprylyl peroxide, di-t-butyl peroxide, ethyl3,3′-di(t-butylperoxy) butyrate, ethyl 3,3′-di(t-amylperoxy) butyrate,t-amylperoxy-2-ethyl hexanoate, and t-butylperoxy pivilate; peresterssuch as t-butyl peracetate, t-butyl perphthalate, and t-butylperbenzoate; as well as percarbonates, such asdi(1-cyano-1-methylethyl)peroxy dicarbonate; perphosphates, and thelike; and combinations thereof.

Polymerization initiators can be used alone or as the oxidizingcomponent of a redox system, which also preferably includes a reducingcomponent such as, e.g., ascorbic acid, malic acid, glycolic acid,oxalic acid, lactic acid, thiogycolic acid, or an alkali metal sulfite,more specifically a hydrosulfite, hyposulfite or metabisulfite, such assodium hydrosulfite, potassium hyposulfite and potassium metabisulfite,or sodium formaldehyde sulfoxylate, and combinations thereof. Thereducing component is frequently referred to as an accelerator or acatalyst activator.

The initiator and accelerator (if any) are preferably used in proportionfrom about 0.001% to 5% each, based on the weight of monomers to becopolymerized. Promoters such as chloride and sulfate salts of cobalt,iron, nickel or copper can be used in small amounts, if desired.Examples of redox catalyst systems include tert-butylhydroperoxide/sodium formaldehyde sulfoxylate/Fe(II), and ammoniumpersulfate/sodium bisulfate/sodium hydrosulfite/Fe(II).

Chain transfer agents can be used to control polymer molecular weight,if desired.

The polymerization reaction of the ethylenically unsaturated monomercomponent in the presence of the aqueous dispersion of thewater-dispersible polymer may be conducted as a batch, intermittent, orcontinuous operation.

Typically, the reactor is charged with an appropriate amount of waterand water-dispersible polymer. Typically, the reactor is then heated tothe free radical initiation temperature and then charged with theethylenically unsaturated monomer component. There may also be somewater miscible solvent present. At temperature, the free radicalinitiator is added and is allowed to react for a period of time atpolymerization temperature, the remaining ethylenically unsaturatedmonomer component (if any) is added incrementally with the rate ofaddition being varied depending on the polymerization temperature, theparticular initiator being employed, and the type and amount of monomersbeing polymerized. After all the monomer component has been charged, afinal heating is carried out to complete the polymerization. The reactoris then cooled and the latex recovered. It should be understood that theabove methodology is only representative and other suitable processesmay also be used.

In some embodiments, the emulsion polymerized ethylenically unsaturatedmonomer component has a Mn of at least about 100,000, at least about200,000, or at least about 300,000. The upper range of the Mn of theemulsion polymerized ethylenically unsaturated monomer component is notrestricted and may be 1,000,000 or more. In certain embodiments,however, the Mn of the emulsion polymerized ethylenically unsaturatedcomponent is less than about 1,000,000, or less than about 600,000.

As previously discussed, in preferred embodiments, the water-dispersiblepolymer and emulsion polymerized ethylenically unsaturated monomercomponent are both present in a latex (e.g., both present in a samelatex particle and/or latex copolymer), which is preferably formed byemulsion polymerizing the ethylenically unsaturated monomer component inthe presence of the water-dispersible polymer. The water-dispersiblepolymer and the emulsion polymerized ethylenically unsaturated monomercomponent may optionally be covalently attached to one another.

Coating compositions of the present invention preferably include atleast a film-forming amount of the resin system described hereincontaining the water-dispersible polymer and the emulsion polymerizedethylenically unsaturated monomer component. In preferred embodiments,the coating composition includes at least about 50 wt-%, more preferablyat least about 65 wt-%, and even more preferably at least about 80 wt-%of the resin system (which is preferably a latex resin system), based onthe solids weight of the water-dispersible polymer and the emulsionpolymerized ethylenically unsaturated monomer component relative to thetotal resin solids weight of the coating composition. The coatingcomposition includes 100 wt-% or less, more typically less than about 99wt-%, and even more typically less than about 95 wt-% of the resinsystem (which is preferably a latex resin system), based on the solidsweight of the water-dispersible polymer and the emulsion polymerizedethylenically unsaturated monomer component relative to the total resinsolids weight of the coating composition. In certain preferredembodiments in which the resin system is a latex-based resin system, thesolids weight of the water-dispersible polymer and the emulsionpolymerized ethylenically unsaturated monomer component is the solidsweight of a latex that functions as the primary film former for thecoating composition.

Typically, resin solids will constitute at least 30 wt-%, at least 40wt-%, or at least 50 wt-% or more of the coating solids. In someembodiments, resin solids constitute all or substantially all (e.g.,greater than 90 or 95 wt-%) of the coating solids.

The coating composition may be formulated from the latex emulsion,optionally with the inclusion of one or more additives and/or byrheological modification for different coating applications (e.g.,diluted for spray coating applications). In embodiments in which thecoating composition includes one or more additives, the additivespreferably do not adversely affect the latex emulsion, or a curedcoating formed from the coating composition. For example, such optionaladditives may be included in the coating composition to enhancecomposition aesthetics, to facilitate manufacturing, processing,handling, and application of the composition, and to further improve aparticular functional property of the coating composition or a curedcoating resulting therefrom.

Such optional additives include, for example, catalysts, dyes, pigments,toners, extenders, fillers, lubricants, anticorrosion agents,flow-control agents, thixotropic agents, dispersing agents,antioxidants, adhesion promoters, light stabilizers, curing agents,co-resins and mixtures thereof. Each optional additive is preferablyincluded in a sufficient amount to serve its intended purpose, but notin such an amount to adversely affect the coating composition or a curedcoating resulting therefrom.

One preferred optional additive is a catalyst to increase the rate ofcure. Examples of catalysts, include, but are not limited to, strongacids (e.g., dodecylbenzene sulphonic acid (DDBSA, available as CYCAT600 from Cytec), methane sulfonic acid (MSA), p-toluene sulfonic acid(pTSA), dinonylnaphthalene disulfonic acid (DNNDSA), and triflic acid),quaternary ammonium compounds, phosphorous compounds, and tin, titanium,and zinc compounds. Specific examples include, but are not limited to, atetraalkyl ammonium halide, a tetraalkyl or tetraaryl phosphonium iodideor acetate, tin octoate, zinc octoate, triphenylphosphine, and similarcatalysts known to persons skilled in the art.

If used, the catalyst is preferably present in an amount of at leastabout 0.01% by weight, and more preferably at least about 0.1% byweight, based on the total solids weight of the coating composition.Furthermore, if used, the catalyst is also preferably present in annon-volatile amount of no greater than about 3% by weight, and morepreferably no greater than about 1% by weight, based on the total solidsweight of the coating composition.

Another useful optional ingredient is a lubricant (e.g., a wax), whichfacilitates manufacture of metal closures and other fabricated coatedarticles by imparting lubricity to sheets of coated metal substrate.Preferred lubricants include, for example, Carnauba wax andpolyethylene-type lubricants. If used, a lubricant is preferably presentin the coating composition in an amount of at least about 0.1% byweight, and preferably no greater than about 2% by weight, and morepreferably no greater than about 1% by weight, based on the total solidsweight of the coating composition.

Another useful optional ingredient is an organosilicon material, such asa siloxane-based and/or polysilicone-based materials. Representativeexamples of suitable such materials are disclosed in InternationalPublication Nos. WO/2014/089410 and WO/2014/186285.

Another useful optional ingredient is a pigment, such as titaniumdioxide. If used, a pigment is present in the coating composition in anamount of no greater than about 70% by weight, more preferably nogreater than about 50% by weight, and even more preferably no greaterthan about 40% by weight, based on the total solids weight of thecoating composition.

The coating composition may also incorporate one or more optional curingagents (e.g., crosslinking resins, sometimes referred to as“crosslinkers”). The choice of particular crosslinker typically dependson the particular product being formulated. For example, some coatingsare highly colored (e.g., gold-colored coatings). These coatings maytypically be formulated using crosslinkers that themselves tend to havea yellowish color. In contrast, white coatings are generally formulatedusing non-yellowing crosslinkers, or only a small amount of a yellowingcrosslinker. Preferred curing agents are substantially free of each ofBPA, BPF, BPS, epoxides thereof (e.g., BADGE), and epoxy novolacs.

Any of the well-known, hydroxyl-reactive curing resins can be used. Forexample, phenoplast, blocked isocyanates, and aminoplast curing agentsmay be used, as well as combinations thereof. In addition, oralternatively, carboxyl-reactive curing resins may be used.

Phenoplast resins include the condensation products of aldehydes withphenols. Formaldehyde and acetaldehyde are preferred aldehydes. Variousphenols can be employed such as phenol, cresol, p-phenylphenol,p-tert-butylphenol, p-tert-amylphenol, and cyclopentylphenol.

Aminoplast resins are the condensation products of aldehydes such asformaldehyde, acetaldehyde, crotonaldehyde, and benzaldehyde with aminoor amido group-containing substances such as urea, melamine, andbenzoguanamine. Examples of suitable aminoplast crosslinking resinsinclude benzoguanamine-formaldehyde resins, melamine-formaldehyderesins, esterified melamine-formaldehyde, and urea-formaldehyde resins.One specific example of a suitable aminoplast crosslinker is the fullyalkylated melamine-formaldehyde resin commercially available from CytecIndustries, Inc. under the trade name of CYMEL 303.

Examples of other generally suitable curing agents are the blocked ornon-blocked aliphatic, cycloaliphatic or aromatic di-, tri-, orpoly-valent isocyanates, such as hexamethylene diisocyanate (HMDI),cyclohexyl-1,4-diisocyanate, and the like. Further examples of generallysuitable blocked isocyanates include isomers of isophorone diisocyanate,dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethanediisocyanate, phenylene diisocyanate, tetramethyl xylene diisocyanate,xylylene diisocyanate, and mixtures thereof. In some embodiments,blocked isocyanates are used that have a number-average molecular weightof at least about 300, more preferably at least about 650, and even morepreferably at least about 1,000.

Other suitable curing agents may include benzoxazine curing agents suchas, for example, benzoxazine-based phenolic resins. Examples ofbenzoxazine-based curing agents are provided in US2016/0297994.

Alkanolamide-type curing agents may also be used. Preferred such curingagents include beta-hydroxyalkyl-amide crosslinkers such as, forexample, those sold under the PRIMID tradename (e.g., the PRIMID XL-552and QM-1260 products) by EMS-CHEMIE AG.

The concentration of the curing agent (e.g., crosslinker) in the coatingcomposition may depend on the type of curing agent, the time andtemperature of the bake, and the molecular weights of the copolymerparticles. If used, the crosslinker is typically present in an amount ofup to about 50% by weight, preferably up to about 30% by weight, andmore preferably up to about 15% by weight. If used, the crosslinker istypically present in an amount of at least about 0.1% by weight, morepreferably at least about 1% by weight, and even more preferably atleast about 1.5% by weight. These weight percentages are based on thetotal resin solids weight of the coating composition.

In some embodiments, the coating composition may be cured without theuse of an external crosslinker (e.g., without phenolic crosslinkers).Additionally, the coating composition may be substantially free offormaldehyde and formaldehyde-containing materials, more preferablyessentially free of these compounds, even more preferably essentiallycompletely free of these compounds, and most preferably completely freeof these compounds.

In preferred embodiments, the coating composition is also substantiallyfree or completely free of any structural units derived from bisphenol A(“BPA”), bisphenol F (“BPF”), and bisphenol S (“BPS”), includingepoxides thereof (e.g., diglycidyl ethers thereof such as the diglycidylether of BPA (“BADGE”)). In addition, the coating composition ispreferably substantially free or completely free of any structural unitsderived from a dihydric phenol, or other polyhydric phenol, havingestrogenic agonist activity great than or equal to that of4,4′-(propane-2,2-diyl)diphenol. More preferably, the coatingcomposition is substantially free or completely free of any structuralunits derived from a dihydric phenol, or other polyhydric phenol, havingestrogenic agonist activity greater than or equal to that of BPS. Insome embodiments, the coating composition is substantially free orcompletely free of any structural units derived from a bisphenol. By wayof example, a structural unit derived from an epoxide of a bisphenol(e.g., a digylcidyl ether of a bisphenol) is considered to be astructural unit derived from a bisphenol.

Even more preferably, the coating composition is substantially free orcompletely free of any structural units derived from a dihydric phenol,or other polyhydric phenol, having estrogenic agonist activity greaterthan 4,4′-(propane-2,2-diyl)bis(2,6-dibromophenol). Optimally, thecoating composition is substantially free or completely free of anystructural units derived from a dihydric phenol, or other polyhydricphenol, having estrogenic agonist activity greater than2,2-bis(4-hydroxyphenyl)propanoic acid. The same is preferably true forany other components of a composition including the coating composition.See, for example, U.S. Publication No. 2013/0316109 for a discussion ofsuch structural units and applicable test methods.

In preferred embodiments, the coating composition is substantially freeor completely free of halogenated monomers (whether free orpolymerized), such as chlorinated vinyl monomers.

The coating composition may also optionally be rheologically modifiedfor different coating applications. For example, the coating compositionmay be diluted with additional amounts of the aqueous carrier to reducethe total solids content in the coating composition. Alternatively,portions of the aqueous carrier may be removed (e.g., evaporated) toincrease the total solids content in the coating composition. The finaltotal solids content in the coating composition may vary depending onthe particular coating application used (e.g., spray coating), theparticular coating use (e.g., for interior can surfaces), the coatingthickness, and the like.

In some embodiments, such as for certain spray coating applications(e.g., inside spray for food or beverage cans including, e.g., aluminumbeverage cans), the coating composition may have a total solids weightgreater than about 5%, more preferably greater than about 10%, and evenmore preferably greater than about 15%, based on the total weight of thecoating composition. In these embodiments, the coating composition mayalso have a total solids weight less than about 40%, more preferablyless than about 30%, and even more preferably less than about 25%, basedon the total weight of the coating composition. In some of theseembodiments, the coating composition may have a total solids weightranging from about 18% to about 22%. The aqueous carrier may constitutethe remainder of the weight of the coating composition.

If desired, the coating composition may also include one or more otheroptional polymers, such as, for example, one or more acrylic polymers,alkyd polymers, epoxy polymers, polyolefin polymers, polyurethanepolymers, polysilicone polymers, polyester polymers, and copolymers andmixtures thereof.

The aqueous carrier of the coating composition includes water and mayfurther include one or more optional organic solvents. In someembodiments, water constitutes greater than about 20% by weight, morepreferably greater than about 35% by weight, and even more preferablygreater than about 50% by weight of the total weight of the aqueouscarrier. In some embodiments, water constitutes 100% or less, morepreferably less than about 95% by weight, and even more preferably lessthan about 90% by weight of the total weight of the aqueous carrier.

While not intending to be bound by theory, the inclusion of a suitableamount of an organic solvent can be advantageous, in some embodiments(e.g., for certain coil coating applications to modify flow and levelingof the coating composition, control blistering, and maximize the linespeed of the coil coater). Accordingly, in certain embodiments, theorganic solvents may constitute greater than 0%, more preferably greaterthan about 5%, and even more preferably greater than about 10% by weightof the aqueous carrier, based on the total weight of the aqueouscarrier. In these embodiments, the organic solvents may also constituteless than about 80%, more preferably less than about 65%, and even morepreferably less than about 50% by weight of the aqueous carrier, basedon the total weight of the aqueous carrier. In some embodiments, organicsolvents constitute less than 40% by weight of the aqueous carrier.

The coating composition preferably has a viscosity suitable for a givencoating application. In some embodiments, the coating composition mayhave an average viscosity greater than about 20 seconds, more preferablygreater than 25 seconds, and even more preferably greater than about 30seconds, based on the Viscosity Test described below (Ford Viscosity Cup#2 at 25° C.). In some embodiments, the coating composition may alsohave an average viscosity less than about 80 seconds, more preferablyless than 60 seconds, and even more preferably less than about 50seconds, based on the Viscosity Test described below (Ford Viscosity Cup#2 at 25° C.).

The coating composition of the present invention may be applied to avariety of different substrates using a variety of different coatingtechniques (e.g., spray coating, roll coating, wash coating, dipping,etc.). In preferred embodiments, the coating composition is applied asan inside spray coating. As briefly described above, cured coatingsformed from the coating composition are particularly suitable for use onmetal food and beverage cans (e.g., two-piece cans, three-piece cans,and the like). Two-piece cans (e.g., two-piece beer or soda cans andcertain food cans) are typically manufactured by a drawn and ironing(“D&I”) process. The cured coatings are also suitable for use in food orbeverage contact situations (collectively referred to herein as“food-contact”), and may be used on the inside or outside of such cans.

Preferred coating compositions of the present invention are particularlysuitable for in forming spray-applied interior coating on aluminum orsteel two-piece draw and ironed beverage or food cans.

The disclosed coating compositions may be present as a layer of amono-layer coating system or as one or more layers of a multi-layercoating system. The coating composition can be used as a primer coat, anintermediate coat, a top coat, or a combination thereof. The coatingthickness of a particular layer and of the overall coating system willvary depending upon the coating material used, the substrate, thecoating application method, and the end use for the coated article.Mono-layer or multi-layer coating systems including one or more layersformed from the disclosed coating composition may have any suitableoverall coating thickness, but will typically have an overall averagedry coating weight of from about 0.6 grams per square meter (“gsm”) toabout 13 gsm and more typically from about 1.0 gsm to about 6.5 gsm.Coating systems for use on closures (e.g., twist-off metal closures) forfood or beverage containers may have an average total coating weight upto about 5.2 gsm. In certain embodiments in which the coatingcomposition is used as an interior coating on a drum (e.g., a drum foruse with food or beverage products), the total coating weight may beapproximately 13 gsm.

The metal substrate used in forming rigid food or beverage cans, orportions thereof, typically has an average thickness in the range ofabout 125 micrometers to about 635 micrometers. Electro-tinplated steel,cold-rolled steel and aluminum are commonly used as metal substrates forfood or beverage cans, or portions thereof. In embodiments in which ametal foil substrate is employed in forming, e.g., a packaging article,the thickness of the metal foil substrate may be even thinner that thatdescribed above.

The disclosed coating compositions may be applied to a substrate eitherprior to, or after, the substrate is formed into an article such as, forexample, a food or beverage container or a portion thereof. In oneembodiment, a method of forming food or beverage cans, or portionsthereof, is provided that includes: applying a coating compositiondescribed herein to a metal substrate (e.g., applying the composition tothe metal substrate in the form of a planar coil or sheet), hardeningthe composition, and forming (e.g., via stamping) the substrate into apackaging container or a portion thereof (e.g., a food or beverage canor a portion thereof). For example, two-piece or three-piece cans orportions thereof such as riveted beverage can ends (e.g., soda or beercans) with a cured coating of the disclosed coating composition on asurface thereof can be formed in such a method. In another embodiment, amethod of forming food or beverage cans is provided that includes:providing a packaging container or a portion thereof (e.g., a food orbeverage can or a portion thereof), applying a coating compositiondescribed herein to the inside, outside or both inside and outsideportions of such packaging container or a portion thereof (e.g., viaspray application, dipping, etc.), and hardening the composition.

After applying the coating composition onto a substrate, the compositioncan be cured using a variety of processes, including, for example, ovenbaking by either conventional or convectional methods, or any othermethod that provides an elevated temperature suitable for curing thecoating. The curing process may be performed in either discrete orcombined steps. For example, substrates can be dried at ambienttemperature to leave the coating compositions in a largely uncrosslinkedstate. The coated substrates can then be heated to fully cure thecompositions. In certain instances, the disclosed coating compositionsmay be dried and cured in one step.

The cure conditions will vary depending upon the method of applicationand the intended end use. The curing process may be performed at anysuitable temperature, including, for example, oven temperatures in therange of from about 100° C. to about 300° C., and more typically fromabout 177° C. to about 250° C. If a metal coil is the substrate to becoated (e.g., metal coil for forming beverage can ends), curing of theapplied coating composition may be conducted, for example, by heatingthe coated metal substrate over a suitable time period to a peak metaltemperature (“PMT”) of preferably greater than about 177° C. Morepreferably, the coated metal coil is heated for a suitable time period(e.g., about 5 to 900 seconds) to a PMT of at least about 218° C.

In some embodiments, the coating composition is an inside spray coatingcomposition capable of being spray applied on an interior of a food orbeverage can (e.g., a 2-piece food or beverage can) to effectively, andevenly, coat the substrate and form a continuous cured coating (i.e., acoating that exhibits a suitably low initial metal exposure value,thereby indicating that the substrate has been effectively coated).

Preferred Tg for the cured coating include those greater than about 50°C., more preferably greater than about 60° C., even more preferablygreater than about 70° C., and in some embodiments, greater than about80° C. Preferred Tg for the cured coating include those less than about120° C., more preferably less than about 115° C., even more preferablyless than about 110° C., and in some embodiments, less than about 100°C. An example of a suitable DSC methodology is provided below.

To further prevent or otherwise reduce coating penetration by anintended food or beverage product, the cured coating is preferablysuitably hydrophobic. For example, the cured coating can have a contactangle with deionized water greater than about 80, more preferablygreater than about 85, and even more preferably greater than about 90,when tested under ambient conditions.

In some embodiments, the cured coating preferably exhibits desiredproperties for use as an interior food-contact coating (e.g., insidespray coating) for food and beverage containers. For example, the curedcoating preferably gives a global extraction of less than about 25parts-per-million (ppm), and more preferably less than about 10 ppm, andeven more preferably less than about 1 ppm, pursuant to the GlobalExtraction test below. Additionally, the cured coating preferablyexhibits a metal exposure less than about 5 milliamps (mA), morepreferably less than about 2 mA, and even more preferably less thanabout 1 mA, pursuant to the Initial Metal Exposure test below.

Flexibility is also important for inside spray coatings, as well asother food or beverage can coatings, so that the coating can deflectwith the metal substrate during post-cure fabrication steps (e.g.,necking and dome reformation) and if the can is dropped from areasonable height during transport or use. In some preferredembodiments, the cured coating preferably exhibits a metal exposure lessthan about 10 mA, more preferably less than about 3.5 mA, even morepreferably less than about 2.5 mA, and optimally less than about 1.5 mA,pursuant to the Metal Exposure After Drop Damage test below.

The coating composition of the present disclosure also offers utility inother coating applications. These additional applications include, butare not limited to, wash coating, sheet coating, and side seam coatings(e.g., food can side seam coatings). Other commercial coatingapplication and curing methods are also envisioned, for example,electrocoating, extrusion coating, laminating, powder coating, and thelike. The coating composition may also be useful in medical or cosmeticpackaging applications, including, for example, on surfaces ofmetered-dose inhalers (“MDIs”), including on drug-contact surfaces.Polymers and coating compositions such as those described in theExamples may be evaluated using a variety of tests including:

1. Viscosity Test

This test measures the viscosity of a latex emulsion or coatingcomposition for rheological purposes, such as for sprayability and othercoating application properties. The test was performed pursuant to ASTMD1200-88 using a Ford Viscosity Cup #2 at 25° C. The results aremeasured in the units of seconds.

2. Curing Conditions

For beverage inside spray bakes, the curing conditions involvemaintaining the temperature measured at the can dome at 180° C. to 225°C. for 60 seconds. For beverage end coil bakes, the curing conditionsinvolve the use of a temperature sufficient to provide a peak metaltemperature within the specified time (e.g., 10 seconds at 204° C. means10 seconds, in the oven, for example, and a peak metal temperatureachieved of 204° C.). The constructions cited were evaluated by tests asfollows.

3. Initial Metal Exposure

This test method determines the amount of the inside surface of the canthat has not been effectively coated by the sprayed coating. Thisdetermination is made through the use of an electrically conductivesolution (1% NaCl in deionized water). The interior “inside spray”coating is typically applied using a high pressure airless spray. Thefollowing minimum film weights are typically used: 0.6 grams per squaremeter (gsm), for a beer can, 1.0 gsm for a soda can, and 1.6 gsm for acan intended for use in packaging a “hard-to-hold” product.

The coated can is filled with this room-temperature conductive solution,and an electrical probe is attached in contact to the outside of the can(uncoated, electrically conducting). A second probe is immersed in theelectrically conductive solution in the middle of the inside of the can.

If any uncoated metal is present on the inside of the can, a current ispassed between these two probes and registers as a value on an LEDdisplay of a suitable measurement apparatus. The LED displays theconveyed currents in milliamps (mA). The current that is passed isdirectly proportional to the amount of metal that has not beeneffectively covered with coating. The goal is to achieve 100% coatingcoverage on the inside of the can, which would result in an LED readingof 0 mA. Preferred coatings give metal exposure values of less than 3mA, more preferred values of less than 2 mA, and even more preferredvalues of less than 1 mA. Commercially acceptable metal exposure valuesare typically less than 2 mA on average.

4. Metal Exposure After Drop Damage

Drop damage resistance measures the ability of the coated container toresist cracks after being in conditions simulating dropping of a filledcan. The presence of cracks is measured by passing electrical currentvia an electrolyte solution, as previously described in the InitialMetal Exposure section. A coated container is filled with theelectrolyte solution (1% NaCl in deionized water) and the initial metalexposure is recorded. The electrolyte solution is removed and the can isthen filled with room-temperature tap water. For two-piece “insidespray” beverage cans, the film weights described in the Initial MetalExposure test can be used.

The water-filled can, which does not include a “top” can end, is droppedthrough a cylindrical tube having a 2 and ⅞ inch (7.3 centimeter)internal diameter, can bottom down, onto an impact wedge (e.g., aninclined plane angled upwards at 33 degrees). The impact wedge ispositioned relative to the tube such that a dent is formed in the rimarea where the can bottom end meets the sidewall (typically referred toas the “chime” of a beverage can). The water-filled can is droppedthrough the tube from a 24-inch (61 centimeter) height (as measuredbetween the can bottom and the point of impact on the impact wedge) ontoan inclined plane, causing a dent in the chime area. The can is thenturned 180 degrees, and the process is repeated.

Water is then removed from the can and metal exposure is again measuredas described above. If there is no damage, no change in current (mA)will be observed relative to the Initial Metal Exposure value.Typically, an average of 6 or 12 container runs is recorded. The metalexposures results for before and after the drop are reported as absolutevalues. The lower the milliamp value, the better the resistance of thecoating to drop damage. Preferred coatings give metal exposure valuesafter drop damage of less than 10 mA, more preferred values of less than3.5 mA, even more preferred values of less than 2.5 mA, and optimalvalues of less than 1.5 mA.

5. Adhesion

Adhesion testing is performed to assess whether the coating adheres tothe coated substrate. The adhesion test was performed according to ASTMD 3359-Test Method B, using SCOTCH 610 tape, available from 3M Companyof Saint Paul, Minn. Adhesion is generally rated on a scale of 0-10where a rating of “10” indicates no adhesion failure (best), a rating of“9” indicates 90% of the coating remains adhered, a rating of “8”indicates 80% of the coating remains adhered, and so on. Adhesionratings of 10 are typically desired for commercially viable coatings.

6. Blush Resistance

Blush resistance measures the ability of a coating to resist attack byvarious solutions. Typically, blush is measured by the amount ofsolution (e.g., water) absorbed into a coated film. When the filmabsorbs water, it generally becomes cloudy or looks white. Blush isgenerally measured visually using a scale of 0-10 where a rating of “10”indicates no blush (best) and a rating of “0” indicates completewhitening of the film (worst). Blush ratings of 7 or higher aretypically desired for commercially viable coatings, and optimally 9-10.

7. Corrosion Resistance

These tests measure the ability of a coating to resist attack bysolutions of different levels of aggressiveness. Briefly, a givencoating is subjected to a particular solution, as described below, andthen measured for adhesion and blush resistance, each also describedbelow. For each test, a result is given using a scale of 0-10, based onthe Adhesion Resistance, Blush Resistance, and/or Blush AdhesionResistance, where a rating of “10” is best and a rating of “0 is worst.

A. Deionized Water

Deionized water is heated to 82° C. Coated panels are immersed in theheated solution for 30 minutes and then removed, rinsed, and dried.Samples are then evaluated for adhesion and blush, as previouslydescribed.

B. Acetic Acid Solution

A 3% solution of acetic acid (C₂H₄O₂) in deionized water is prepared andheated to 100° C. Coated panels are immersed in the heated solution for30 minutes and then removed, rinsed, and dried. Samples are thenevaluated for adhesion and blush, as previously described.

C. Citric Acid Solution

A 2% solution of citric acid (C6H807) in deionized water is prepared andheated while subjected to a pressure sufficient to achieve a solutiontemperature of 121° C. Coated panels are immersed in the heated solutionfor 30 minutes and then removed, rinsed, and dried. Samples are thenevaluated for adhesion and blush, as previously described.

8. Pasteurization

The pasteurization test determines how a coating withstands theprocessing conditions for different types of food products packaged in acontainer. Typically, a coated substrate is immersed in a water bath andheated for 5-60 minutes at temperatures ranging from 65° C. to 100° C.For the present evaluation, the coated substrate was immersed in eithera deionized water bath for 45 minutes at 85° C., or a 3% solution ofacetic acid (C₂H₄O₂) in deionized water for 30 minutes to 100° C. Coatedpanels are immersed in the heated solution for 30 minutes. The coatedsubstrate is then removed from the bath and tested for coating adhesionand blush as described above. Commercially viable coatings preferablyprovide adequate pasteurization resistance with perfect adhesion (ratingof 10) and blush ratings of 5 or more, optimally 9-10.

9. Glass Transition Temperature (“Tg”)

Samples for differential scanning calorimetry (“DSC”) testing may beprepared by first applying the liquid resin composition onto aluminumsheet panels. The panels are then baked in a Fisher Isotemp electricoven for 20 minutes at 300° F. (149° C.) to remove volatile materials.After cooling to room temperature, the samples are scraped from thepanels, weighed into standard sample pans and analyzed using thestandard DSC heat-cool-heat method. The samples are equilibrated at −60°C., then heated at 20° C. per minute to 200° C., cooled to −60° C., andthen heated again at 20° C. per minute to 200° C. Glass transitions arecalculated from the thermogram of the last heat cycle. The glasstransition is measured at the inflection point of the transition.

10. Global Extraction

The global extraction test is designed to estimate the total amount ofmobile material that can potentially migrate out of a coating and intofood packed in a coated can. Typically coated substrate is subjected towater or solvent blends under a variety of conditions to simulate agiven end use. Acceptable extraction conditions and media can be foundin 21 CFR § 175.300 paragraphs (d) and (e). The allowable globalextraction limit as defined by the FDA regulation is 50 parts permillion (ppm).

The extraction procedure used in the current invention is described in21 CFR § 175.300 paragraph (e)(4)(xv) with the following modificationsto ensure worst-case scenario performance: (1) the alcohol (ethanol)content was increased to 10% by weight, and (2) the filled containerswere held for a 10-day equilibrium period at 37.8° C. (100° F.). Theseconditions are per the FDA publication “Guidelines for Industry” forpreparation of Food Contact Notifications.

The coated beverage can is filled with 10% by weight aqueous ethanol andsubjected to pasteurization conditions (65.6° C., 150° F.) for 2 hours,followed by a 10-day equilibrium period at 37.8° C. (100° F.).Determination of the amount of extractives is determined as described in21 CFR § 175.300 paragraph (e) (5), and ppm values were calculated basedon surface area of the can (no end) of 44 square inches with a volume of355 milliliters. Preferred coatings give global extraction results ofless than 50 ppm, more preferred results of less than 10 ppm, and evenmore preferred results of less than 1 ppm. Most preferably, the globalextraction results are optimally non-detectable.

EXAMPLES

The present disclosure is more particularly described in the followingexamples that are intended as illustrations only, since numerousmodifications and variations within the scope of the present disclosurewill be apparent to those skilled in the art. Unless otherwiseindicated, all parts and percentages are by weight.

Example 1: BPA-Free and Styrene-Free Water-DispersiblePolyether-Acrylate Copolymer

To a reaction vessel equipped with a stirrer, reflux condenser,thermocouple, heating and cooling capability, and inert gas blanket,477.4 parts of the digylcidyl ether of tetramethyl bisphenol F and 114.2parts hydroquinone were added. Then 0.59 parts ethyltriphenylphosphonium iodide and 13.9 parts carbitol were added. The system washeated to 130° C. under an inert atmosphere. Once exothermic activitywas observed and peaked, temperature was set to 165° C. for 75 minutesor until target epoxy value of 0.039 equivalents per 100 gram solidresin was achieved. At epoxy value, 156.8 parts 2-butoxyethanol wasadded slowly followed by 90.6 parts n-butanol and 65.9 parts amylalcohol. The temperature was allowed to drift to a set point of 110° C.To the reaction vessel a premix of 117.4 parts methacrylic acid, 41.8parts n-butyl methacrylate, 62.7 parts ethyl methacrylate, 31.2 partsethyl acrylate, 6.4 parts azobisisobutyronitrile, and 6.4 partstert-butyl peroctoate was added over 90 minutes to maintain thetemperature under 115° C. Once addition was complete 66.4 parts2-butoxyethanol and 1.7 parts tert-butyl peroctoate was added and thetemperature was held at 110° C. for 50 minutes. At the end of the holdtime, an additional 0.6 parts tert-butyl peroctoate was added and thetemperature was held for 40 minutes. Once the hold time was complete,the reactor set point was set to 95° C., agitation was increased, andthe temperature was allowed to drift from 110° C. to 95° C. while 89.4parts of deionized water over 10 minutes. At temperature, 56.4 partsdimethyl ethanolamine was added over 5 minutes, followed by a 30 minutehold. For the dispersion step, 782.6 parts deionized water was added tothe vessel over 50 minutes while heating was removed and the temperaturewas allowed to drift down. Following the water charge, a second chargingof 1230.9 parts of deionized water was added over 30 minutes.

Example 2: BPA-Free and Styrene-Free Latex and Coating Composition

Immediately following completion of the above steps for Example 1, theresulting material of Example 1 was provided and the heat wasreinitiated to a set point of 75° C., at temperature a premix of 148.1parts n-butyl methacrylate, 185.2 parts ethyl methacrylate, and 37.0parts n-butyl acrylate was added over 20 minutes. Once added,temperature was increased to a set point of 82° C. At temperature 2.9parts benzoin, 2.9 parts hydrogen peroxide, and 4.6 parts deionizedwater were added and the temperature was held for 120 minutes. Anadditional 0.8 parts benzoin, 0.8 parts hydrogen peroxide, and 4.3 partsdeionized water were added and the temperature was held for 60 minutes.The process yielded a material at 31.5% solids, a Brookfield viscosityof 2032 centipoise (cps), an acid number of 58.9, a pH of 6.7, and aparticle size of 0.19 micron.

To produce a finish coating composition, 159.3 parts 2-butoxyethanol,200.3 parts amyl alcohol, and 1.7 parts n-butanol were charged to thevessel. The process yielded a material of ˜19.2% solids and a #2 FordCup viscosity of 39.0 seconds.

Comparative Example A: BPA-Free, Styrene-Containing Latex

To a reaction vessel equipped with a stirrer, reflux condenser,thermocouple, heating and cooling capability, and inert gas blanket,499.5 parts of the digylcidyl ether of tetramethyl bisphenol F and 118.6parts hydroquinone were added. Then 0.96 parts ethyltriphenylphosphonium iodide and 40.1 parts 2-butoxyethanol were added. The systemwas heated to 130° C. under an inert atmosphere. Once exothermicactivity was observed and peaked, temperature was set to 165° C. for 60minutes or until target epoxy value of 0.039 equivalents per 100 gramsolid resin was achieved. At epoxy value, 14.8 parts 2-hexoxyethanol wasadded slowly followed by 60.6 parts n-butanol. To the reaction vessel apre-reacted solution acrylic composed of 68.2 parts acrylic acid, 43.9parts methacrylic acid, 87.8 parts styrene, 50.0 parts ethyl acrylate,19.1 parts deionized water, 26.1 parts n-butanol, 194.3 parts n-amylalcohol, and 8.9 parts 2-hexoxyethanol was added over 60 minutes and thetemperature maintained at 110° C. Once all pre-reacted solution acrylicwas added, the solution was allowed to mix for a minimum of 20 minutes.Following a hold, 38.2 parts dimethyl ethanolamine was added over 3 to 5minutes followed by a 60 minute hold. At the end of the hold, 18.2 partsdimethyl ethanolamine added and held for 15 minutes. For the dispersionstep, 2,111.7 parts deionized water was added to the vessel over 90minutes while the temperature was allowed to drift to 80° C. The heatwas reinitiated to a set point of 80° C. At temperature, a premix of147.6 parts styrene, 146.7 parts n-butyl acrylate, and 3.0 parts benzoinwas added to the dispersion. Once added, the temperature was increasedto a set point of 84° C. At temperature 3.0 parts hydrogen peroxide and4.5 parts deionized water were added and the temperature was held for120 minutes. Following hold, an additional 73.7 parts styrene, 0.7 partsbenzoin, 0.7 parts hydrogen peroxide, and 4.3 parts deionized water wereadded and the temperature was held for 180 minutes. The process yieldeda material of 32.7% solids, at Brookfield viscosity of 1068 cps, a pH of6.7, and a particle size of 0.14 micron.

To prepare a finish coating composition, 159.3 parts 2-butoxyethanol,200.3 parts amyl alcohol, and 1.7 parts n-butanol were charged to thevessel. The process yielded a material of 20.0% solids and #2 Ford Cupviscosity of 36 seconds.

Comparative Example B: BPA and Styrene-Containing Latex

A commercial BPA- and styrene-containing water-based beverage insidespray composition was provided. The composition was a latex-basedcoating composition in which the latex includes water-dispersible BPA-and styrene-containing aromatic polyether-acrylate copolymerover-polymerized (i.e., emulsion polymerized) with an ethylenicallyunsaturated monomer component including a substantial amount of styrene.

Example 3: BPA-Free and Styrene-Free Latex Including High Level ofMethyl Methacrylate In Ethylenically Unsaturated Monomer Component

To a reaction vessel equipped with a stirrer, reflux condenser,thermocouple, heating and cooling capability, and inert gas blanket,125.6 parts of the digylcidyl ether of tetramethyl bisphenol F and 30.0parts hydroquinone were added. Then 0.15 parts ethyltriphenylphosphonium iodide and 3.7 parts carbitol were added. The system washeated to 130° C. under an inert atmosphere. Once exothermic activitywas observed and peaked, the temperature was set to 165° C. for 75minutes or until target epoxy value of 0.039 Equivalent per 100 gramsolid resin was achieved. At epoxy value, 41.1 parts 2-butoxyethanol wasadded slowly followed by 34.5 parts n-butanol and 6.7 parts2-hexoxyethanol. The temperature was allowed to drift to a set point of110° C. To the reaction vessel, a premix of 11.7 parts methacrylic acid,18.7 parts acrylic acid, 23.4 parts methyl methacrylate, 13.3 partsethyl acrylate, 1.7 parts azobisisobutyronittile, and 1.7 partstert-butyl peroctoate was added over 90 minutes to maintain thetemperature under 115° C. Once addition was complete, 17.5 parts2-butoxyethanol and 0.4 parts test-butyl peroctoate was added and thetemperature was held at 110° C. for 50 minutes. At the end of the holdtime, an additional 0.2 parts tert-butyl peroctoate was added and thetemperature was held for 40 minutes. Once the hold time was complete,the reactor set point was set to 95° C., agitation was increased, andtemperature was allowed to drift from 110° C. to 95° C. while 23.5 partsdeionized water was added over 10 minutes. At temperature, 14.8 partsdimethyl ethanolamine was added over 5 minutes followed by a 30 minutehold. For the dispersion step, 206.0 parts deionized water was added tothe vessel over 50 minutes while the temperature was allowed to driftdown and heating was removed. Following the water charge, a secondcharging of 323.9 parts of deionized water was added over 30 minutes.The heat was reinitiated to a set point of 55° C., at temperature apremix of 68.2 parts methyl methacrylate and 29.2 parts n-butyl acrylatewas added over 20 minutes. At temperature, 0.5 parts tert-amylhydroperoxide (85% in water) and the reaction was held for 5 minutes.Following a brief hold, a premix of 0.3 parts erythorbic acid, 3.1 partsdeionized water, 0.3 parts dimethyl ethanolamine, and 0.03 parts of aniron sulfate solution were added over 30 minutes. Following feed, somephase separation was observed, and the system was stirred untilhomogeneous. The process yielded a material of 31.6% solids, aBrookfield viscosity of 19,500 cps, and a particle size of 0.25 micron.

To prepare a finish coating composition, 10.1 parts 2-butoxyethanol,50.3 parts amyl alcohol, and 0.4 parts n-butanol were charged to thevessel. The process yielded a material of ˜17.8% solids and a #2 FordCup viscosity of 60 seconds.

Coating Performance Data

To assess the coating performance properties of the various systems, thecoating compositions referenced in the below Tables 1-3 were sprayedapplied onto the interior surfaces of standard 12 ounce two-piecealuminum D&I beverage cans at a dry film weight of 115 milligrams percan. The cans were baked for at least 50 seconds at an oven temperatureof at least 370° F. (188° C.) to achieve a dome peak metal temperatureof at least 390° F. (199° C.). The coated cans were then subjected tothe various tests referenced in Tables 1-3.

As can be seen from the data, the coating composition of Example 2performed similar to the commercial BPA- and styrene-containing insidespray product of Comparative Example B. It also performed similar to theBPA-free, styrene-containing latex of Comparative Example A. The coatingcomposition of Example 2 performed notably better than Example 3, whichdid not include more than 30 weight percent of monomers A in theemulsion polymerized ethylenically unsaturated monomer component. Thus,as discussed throughout herein, in preferred embodiments the emulsionpolymerized ethylenically unsaturated monomer component includes morethan 30 weight percent of one or more monomers A.

TABLE 1 Blush Adhesion Liquid Liquid 3% Acetic Acid Dome/Side VaporDome/Side Vapor −30′ @ 212° F. Wall Side Wall Wall Side Wall Example 29/9 10 10/10 10 Comparative 10/10 10 10/10 10 Example A Comparative10/10 10 10/10 10 Example B Example 3 10/10 10 10/10 10

TABLE 2 Blush Adhesion Liquid Vapor Liquid Vapor 2% Citric AcidDome/Side Side Dome/Side Side −30′ @ 250° F. Wall Wall Wall Wall Example2 6/6 10 10/10 10 Comparative 8/8 10 10/10 10 Example A Comparative 7/710 10/10 10 Example B Example 3 7/5 9 0/0 7

TABLE 3 Drop Can Average Final M.E. Drop Δ M.E. (mA) (mA) Example 2 0.80.3 Comparative Example A 0.6 0.2 Comparative Example B 0.4 0.2 Example3 2.4 10.0

A BPA-free and styrene-free latex and coating composition similar tothat of Example 2 was also made where the water-dispersiblepolyether-acrylate was made using a preformed organic-solutionpolymerized acid-functional acrylic instead of an in situ polymerizedacrylic as in Example 1. The preformed acrylic and aromatic polyetherpolymer were reacted together in the presence of a tertiary amine andthen dispersed into water. The coating composition exhibited comparablecoating performance properties in a food or beverage can coating end userelative to that of Example 2.

The complete disclosure of all patents, patent applications, andpublications (including material safety data sheets, technical datasheets and product brochures for the raw materials and ingredients usedin the Examples), and electronically available material cited herein areincorporated herein by reference as if individually incorporated. Theforegoing detailed description and examples have been given for clarityof understanding only. No unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed, for variations obvious to one skilled in the art will beincluded within the invention defined by the claims. The inventionillustratively disclosed herein suitably may be practiced, in someembodiments, in the absence of any element which is not specificallydisclosed herein.

What is claimed is:
 1. An aqueous food or beverage can coatingcomposition suitable for use in forming a food-contact coating for ametal food or beverage can, the coating composition comprising: anaqueous carrier; and a resin system dispersed in the aqueous carrier,wherein the resin system is substantially free of styrene and comprises:a water-dispersible polyether polymer; and an emulsion polymerizedethylenically unsaturated monomer component comprising at least 80 wt-%of one or more of methyl methacrylate, ethyl acrylate, ethylmethacrylate, butyl acrylate, and butyl methacrylate; wherein thecoating composition has a viscosity of from 20 to 80 seconds (Ford Cup#2, 25° C.) and is an inside spray coating composition for a food orbeverage can.
 2. The coating composition of claim 1, wherein theemulsion polymerized ethylenically unsaturated monomer componentcomprises at least 80 wt-% of one or more of methyl methacrylate, ethylacrylate, ethyl methacrylate, n-butyl acrylate, and n-butylmethacrylate.
 3. The coating composition of claim 2, wherein: theemulsion polymerized ethylenically unsaturated monomer componentcomprises at least 80 wt-% of: (i) one or more of methyl methacrylate,ethyl acrylate, ethyl methacrylate and (ii) one or more of n-butylacrylate and n-butyl methacrylate; and wherein the emulsion polymerizedethylenically unsaturated monomer component includes less than 40 wt-%,if any, of methyl methacrylate.
 4. The coating composition of claim 1,wherein the water-dispersible polyether polymer comprises an aromaticpolyether polymer that is substantially free of each of bisphenol A,bisphenol F, and bisphenol S, including epoxides thereof.
 5. The coatingcomposition of claim 4, wherein the aromatic polyether polymer has glasstransition temperature of at least 60° C. and a number average molecularweight of at least 2,000.
 6. The coating composition of claim 4, whereinthe aromatic polyether polymer is formed from reactants including anextender and a diepoxide, and wherein the diepoxide comprises adiepoxide of an aromatic diol, an aromatic diacid, an aliphatic diol, analiphatic diacid, a cycloaliphatic diol, a cycloaliphatic diacid, or acombination thereof.
 7. The coating composition of claim 6, wherein thearomatic polyether polymer is formed from reactants including anextender and a diepoxide of 2,2,4,4-tetramethyl-1,3-cyclobutanediol oran extender and a diepoxide of 2,2,4,4-tetramethyl-1,3-cyclobutanedicarboxylic acid.
 8. The coating composition of claim 4, wherein thewater-dispersible polyether polymer comprises a polyether-acrylatecopolymer.
 9. The coating composition of claim 1, wherein thewater-dispersible polyether polymer comprises an aromatic polyetherpolymer formed from reactants including an extender and a diepoxide, andwherein the diepoxide comprises a diepoxide of an ortho-substituteddiphenol.
 10. The coating composition of claim 9, wherein the diepoxideof the ortho-substituted diphenol comprises a diglycidyl ether oftetramethyl bisphenol F.
 11. The coating composition of claim 1, whereinthe water-dispersible polyether polymer comprises an aromatic polyetherpolymer that is substantially free of any structural units derived froma bisphenol.
 12. The coating composition of claim 1, wherein thewater-dispersible polyether polymer has an acid number from 40 to 400 mgKOH per gram, and wherein the total combined weight of thewater-dispersible polyether polymer and the emulsion polymerizedethylenically unsaturated monomer component is at least 50 wt-% of thetotal resin solids present in the coating composition.
 13. The coatingcomposition of claim 1, wherein the emulsion polymerized ethylenicallyunsaturated monomer component further comprises one or moreethylenically unsaturated monomers having a cycloaliphatic group. 14.The coating composition of claim 13, wherein the cycloaliphatic groupcomprises a polycyclic group.
 15. The coating composition of claim 13,wherein the one or more ethylenically unsaturated monomers having acycloaliphatic group comprise cyclohexyl (meth)acrylate,4-tert-butylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl(meth)acrylate, isobornyl (meth)acrylate, tetrahydrofurfuryl(meth)acrylate, an isomer thereof, or a mixture thereof.
 16. The coatingcomposition of claim 1, wherein the emulsion polymerized ethylenicallyunsaturated monomer component has a Tg of at least 40° C.
 17. Thecoating composition of claim 1, wherein the coating composition, whenspray applied onto an interior of a standard 12 ounce aluminum drawn &ironed beverage can at a dry film weight of 115 milligrams per can andbaked for at least 50 seconds at an oven temperature of at least 188° C.to achieve a dome peak metal temperature of at least 199° C., exhibits alower sidewall adhesion rating value of 9 or 10 after retort in 2%citric acid under pressure at 121° C. and tested according to ASTM D3359—Test Method B, using SCOTCH 610 tape, available from 3M Company ofSaint Paul, Minn.
 18. The coating composition of claim 1, wherein thecoating composition, when spray applied onto an interior of a standard12 ounce aluminum drawn & ironed beverage can at a dry film weight of115 milligrams per can and baked for at least 50 seconds at an oventemperature of at least 188° C. to achieve a dome peak metal temperatureof at least 199° C., exhibits a contact angle with deionized watergreater than about
 80. 19. The coating composition of claim 1, whereinthe resin system is also substantially free of substituted styrenecompounds.
 20. The coating composition of claim 1, wherein theethylenically unsaturated monomer component is emulsion polymerized inthe presence of the aqueous dispersion of the water-dispersiblepolyether polymer.
 21. A food or beverage can, or a portion thereof,having a cured interior food-contact coating formed from the coatingcomposition of claim
 1. 22. An aqueous food or beverage can coatingcomposition suitable for use in forming a food-contact coating for ametal food or beverage can, the coating composition comprising: anaqueous carrier; and a resin system dispersed in the aqueous carrier,wherein the resin system is substantially free of styrene and comprises:a water-dispersible a polyether polymer, wherein the wherein thewater-dispersible polyether polymer includes one or moreammonia-neutralized or amine-neutralized acid or anhydride groups; andan emulsion polymerized ethylenically unsaturated monomer componentcomprising at least 80 wt-% of one or more of methyl methacrylate, ethylacrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate;wherein the weight ratio of water-dispersible polyether polymer toemulsion polymerized ethylenically unsaturated monomer component is from40:60 to 90:10, wherein the total combined weight of thewater-dispersible polyether polymer and the emulsion polymerizedethylenically unsaturated monomer component is at least 50 wt-% of thetotal resin solids present in the coating composition, and wherein thecoating composition has a viscosity of from 20 to 80 seconds (Ford Cup#2, 25° C.) and is an inside spray coating composition for a food orbeverage can.
 23. The coating composition of claim 22, wherein thecoating composition, when spray applied onto an interior of a standard12 ounce aluminum drawn & ironed beverage can at a dry film weight of115 milligrams per can and baked for at least 50 seconds at an oventemperature of at least 188° C. to achieve a dome peak metal temperatureof at least 199° C., exhibits a contact angle with deionized watergreater than about 80.